Calibration for multi-stage physiological monitors

ABSTRACT

A physiological monitor is provided for determining a physiological parameter of a medical patient with a multi-stage sensor assembly. The monitor includes a signal processor configured to receive a signal indicative of a physiological parameter of a medical patient from a multi-stage sensor assembly. The multi-stage sensor assembly is configured to be attached to the physiological monitor and the medical patient. The monitor of certain embodiments also includes an information element query module configured to obtain calibration information from an information element provided in a plurality of stages of the multi-stage sensor assembly. In some embodiments, the signal processor is configured to determine the physiological parameter of the medical patient based upon said signal and said calibration information.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/960,325, filed Dec. 3, 2010, and titled “Calibration For Multi-StagePhysiological Monitors,” which application claims priority from U.S.Provisional Patent Application No. 61/266,984, filed Dec. 4, 2009, andtitled “Automatic Calibration for Multi-Stage Physiological Monitors.”The disclosures of all of the above-referenced applications are herebyincorporated by reference herein in their entireties and for allpurposes.

Additionally, this application relates to the following U.S. patentapplications, the disclosures of which are incorporated in theirentirety by reference herein:

App. No. Filing Date Title Attorney Docket 60/893,853 Mar. 08, 2007MULTI-PARAMETER MCAN.014PR PHYSIOLOGICAL MONITOR 60/893,850 Mar. 08,2007 BACKWARD COMPATIBLE MCAN.015PR PHYSIOLOGICAL SENSOR WITHINFORMATION ELEMENT 60/893,858 Mar. 08, 2007 MULTI-PARAMETER SENSOR FORMCAN.016PR PHYSIOLOGICAL MONITORING 60/893,856 Mar. 08, 2007PHYSIOLOGICAL MONITOR WITH MCAN.017PR FAST GAIN ADJUST DATA ACQUISITION12/044,883 Mar. 08, 2008 SYSTEMS AND METHODS FOR MCAN.014A DETERMINING APHYSIOLOGICAL CONDITION USING AN ACOUSTIC MONITOR 61/252,083 Oct. 15,2009 DISPLAYING PHYSIOLOGICAL MCAN.019PR INFORMATION 12/904,836 Oct. 14,2010 BIDIRECTIONAL PHYSIOLOGICAL MCAN.019A1 INFORMATION DISPLAY12/904,823 Oct. 14, 2010 BIDIRECTIONAL PHYSIOLOGICAL MCAN.019A2INFORMATION DISPLAY 61/141,584 Dec. 30, 2008 ACOUSTIC SENSOR ASSEMBLYMCAN.030PR 61/252,076 Oct. 15, 2009 ACOUSTIC SENSOR ASSEMBLY MCAN.030PR212/643,939 Dec. 21, 2009 ACOUSTIC SENSOR ASSEMBLY MCAN.030A 61/313,645Mar. 12, 2010 ACOUSTIC RESPIRATORY MCAN.033PR2 MONITORING SENSOR HAVINGMULTIPLE SENSING ELEMENTS 12/904,931 Oct. 14, 2010 ACOUSTIC RESPIRATORYMCAN.033A MONITORING SENSOR HAVING MULTIPLE SENSING ELEMENTS 12/904,890Oct. 14, 2010 ACOUSTIC RESPIRATORY MCAN.033A2 MONITORING SENSOR HAVINGMULTIPLE SENSING ELEMENTS 12/904,938 Oct. 14, 2010 ACOUSTIC RESPIRATORYMCAN.033A3 MONITORING SENSOR HAVING MULTIPLE SENSING ELEMENTS 12/904,907Oct. 14, 2010 ACOUSTIC PATIENT SENSOR MCAN.033A4 61/252,062 Oct. 15,2009 PULSE OXIMETRY SYSTEM WITH MCAN.035PR LOW NOISE CABLE HUB61/265,730 Dec. 01, 2009 PULSE OXIMETRY SYSTEM WITH MCAN.035PR3 ACOUSTICSENSOR 12/904,775 Oct. 14, 2010 PULSE OXIMETRY SYSTEM WITH MCAN.035A LOWNOISE CABLE HUB 12/905,036 Oct. 14, 2010 PHYSIOLOGICAL ACOUSTICMCAN.046A MONITORING SYSTEM 61/331,087 May 04, 2010 ACOUSTIC RESPIRATIONDISPLAY MASIMO.800PR2 61/391,098 Oct. 08, 2010 ACOUSTIC MONITORMCAN-P001

BACKGROUND

Hospitals, nursing homes, and other patient care facilities typicallyinclude patient monitoring devices at one or more bedsides in thefacility. Patient monitoring devices generally include sensors,processing equipment, and displays for obtaining and analyzing a medicalpatient's physiological parameters. Physiological parameters include,for example, respiratory rate, oxygen saturation (SpO₂) level, pulse,and blood pressure, among others. Clinicians, including doctors, nurses,and certain other medical personnel, use the physiological parametersobtained from the medical patient to diagnose illnesses and to prescribetreatments. Clinicians also use the physiological parameters to monitora patient during various clinical situations to determine whether toincrease the level of medical care given to the patient.

Many monitoring devices receive physiological signals from one or moresensors, such as pulse oximetry sensors, other types of optical sensors,acoustic sensors, and the like. Medical cables attached to the sensorstransmit signals from the sensors to the monitoring device.

Physiological signals in some monitoring systems can be relatively smallor otherwise difficult to measure with a high degree of accuracy. Assuch, manufacturing tolerances for the various components in the systemmay be relatively tight, possibly leading to low yields, increasedmanufacturing cost and/or reduced flexibility in component design.

Additionally, sensors, cables and other components in the sensor pathmay be sold with a specific monitoring device and are factory calibratedfor use with only that monitoring device, reducing flexibility incomponent selection. Alternatively, some systems may be manuallycalibrated in the field, increasing cost and setup time. Accordingly,there remains a need for a monitoring system capable of providingaccurate physiological measurement while addressing these and otherissues.

SUMMARY

According to certain aspects, a physiological monitor is provided fordetermining a physiological parameter of a medical patient with amulti-stage sensor assembly. The physiological monitor can include asignal processor configured to receive a signal indicative of aphysiological parameter of a medical patient from a multi-stage sensorassembly. The multi-stage sensor assembly can be configured to beattached to the physiological monitor and the medical patient. Thephysiological monitor can further include an information element querymodule configured to obtain calibration information from an informationelement provided in a plurality of stages of the multi-stage sensorassembly. In certain embodiments, the signal processor is configured todetermine the physiological parameter of the medical patient based uponsaid signal and said calibration information.

A method of determining a physiological parameter of a medical patientwith a physiological monitor is provided according to certain aspects.The method may include receiving a signal indicative of a physiologicalparameter of a medical patient from a multi-stage sensor assembly. Insome embodiments, the method further includes obtaining calibration froman information element provided in a plurality of stages of themulti-stage sensor assembly. The method can further include determiningthe physiological parameter of the medical patient based upon the signaland the calibration information.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments will be described hereinafter with reference to theaccompanying drawings. These embodiments are illustrated and describedby example only, and are not intended to limit the scope of thedisclosure. In the drawings, similar elements have similar referencenumerals.

FIG. 1 illustrates a perspective view of an embodiment of aphysiological monitoring system;

FIG. 2 is a top perspective view illustrating an embodiment of anexample sensor assembly and cable;

FIGS. 3A and 3B illustrate block diagrams of example monitoring systemsthat include one or more information elements usable for multi-stagecalibration, according to certain embodiments;

FIG. 3C illustrates an embodiment of a circuit for communicating withone or more information elements and a sensor;

FIG. 4 illustrates a block diagram showing calibration information andother exemplary forms of data that can be stored in an informationelement;

FIG. 5 illustrates a functional block diagram of an embodiment of aphysiological monitoring system configurable to perform multi-stagecalibration according to certain embodiments;

FIG. 6 illustrates a flowchart diagram of an example physiologicalmonitoring process implementing multi-stage calibration according tocertain embodiments;

FIGS. 7A and 7B illustrate block diagrams of example physiologicalmonitoring systems having splitter cables;

FIG. 8 illustrates a block diagram of another embodiment of aphysiological monitoring system having multiple cables;

FIG. 9 illustrates a block diagram of yet another embodiment of aphysiological monitoring system having multiple cables;

FIGS. 10A through 10C illustrate embodiments of decoupling circuits;

FIG. 11A illustrates a side view of an example splitter cable;

FIG. 11B illustrates a bottom view of the example splitter cable of FIG.6A;

FIG. 12 illustrates a perspective view of an example sensor and cableassembly;

FIG. 13 illustrates an embodiment of a physiological monitoring systemhaving multiple networked physiological monitors;

FIGS. 14 and 15 illustrate flowchart diagrams of example cablemanagement processes;

FIGS. 16 and 17 illustrate flowchart diagrams of example patient contextmanagement processes;

FIG. 18 illustrates an embodiment of a coextruded cable; and

FIG. 19 illustrates an embodiment of a splitter cable.

DETAILED DESCRIPTION

Systems described herein include various components, such as one or morecables, front end processing circuitry, and the like, interposed in thepath between the sensor and signal processing circuitry in a monitoringdevice. The sensor and these components or portions thereof may bedescribed as stages in the sensor path. Systems described herein mayaccordingly be referred to as multi-stage systems.

Multi-Stage Calibration Overview

Each stage in the sensor path has particular behavioral characteristicsdefining a response for that stage. Generally, each stage receives aversion of the detected sensor signal and produces a modified version ofthat signal according to a characteristic response of the respectivestage. The behavioral characteristics defining the characteristicresponses of the stages can include a variety of parameters such aselectrical properties (e.g., capacitances, impedances, etc.), mechanicalproperties, response characteristics (e.g., frequency responses, gaincharacteristics, etc.), among others. Information relating to thesecharacteristics may be referred to through this disclosureinterchangeably as calibration information, behavioral information andbehavioral characteristic information, for example.

Due to inconsistencies in manufacture, materials, etc., certainbehavioral characteristics and corresponding calibration information canvary significantly between components of the same type. Characteristicssubject to these types of inconsistencies may be referred to as processvariable characteristics as they are dependent on material ormanufacturing inconsistencies. It is generally desirable for amonitoring system to be able to cooperate with components having as widea range of process variable characteristics as possible. For example,manufacturing tolerances can be expanded as a result, leading toimproved accuracy and repeatability, higher yields and reduced cost.

In addition to process variable characteristics, design variablecharacteristics can arise based on various component design schemes andassociated parameters. Because they are based on known design choices,design variable characteristics are generally predetermined, unlikeprocess variable characteristics.

As one example of a scenario involving design variable characteristics,an acoustic sensor of a first design scheme may include designcharacteristics optimized to use relatively low amplitude signals, suchas for use with patients having a particularly shallow breath or todetect a certain type of relatively quiet physiological sound. Designchoices for this sensor are tailored for such a use. For example, arelatively sensitive material may be used for the sensing element (e.g.,a piezoelectric film), or the sensing element may be manufactured forrelatively high sensitivity. Moreover, programmable variables such asgain settings may be set to a relatively high level. On the other hand,an acoustic sensor according to a second design may be optimized todetect relatively louder physiological sounds. For this sensor,different design parameters are used such as a relatively less sensitivesensing element, lower gain settings, etc. Beyond this illustrativeexample, a broad universe of design variable characteristics associatedwith monitoring systems exists, such as design variable characteristicsassociated with non-sensor components (e.g., cables, processingcircuitry, etc.) or those related to other types of sensors (e.g.,optical sensors such as SpO₂ sensors).

It is desirable for monitoring systems to be able to adapt to componentshaving generally as wide a range of design variable characteristics aspossible. For example, this can allow system designers to develop anarray of components that are customized for particular applications.

Systems described herein are advantageously capable of accounting forprocess characteristic variability and/or design characteristicvariability, allowing for system calibration (e.g., automaticcalibration) based on the properties of the particular attachedcomponents. This calibration technique may be referred tointerchangeably throughout this disclosure as automatic, dynamic,adaptive, or intelligent calibration. In some embodiments, the processmay also be referred to as sensor path or signal acquisition, or ashaving an equalization effect on the sensor signal, for example. Theseterms are used for the purpose of illustration and are not intended tobe limiting. In some other embodiments, at least a portion of thecalibration process is achieved manually.

According to some embodiments, one or more of the stages in the sensorpath has at least one information element storing calibrationinformation relating to that stage. The calibration information may bedetermined and stored, such as during manufacture. For example, a testsignal may be injected into a component such as a physiological sensor.Various characteristics such as frequency responses, capacitances, etc.,of the sensor may be measured using the test signal and are stored in aninformation element on the sensor. Additionally, certain predeterminedcharacteristics, which may primarily include design variablecharacteristics, may be stored on the information element without anyseparate calibration process.

According to certain embodiments, the monitoring device is configured toreceive the calibration information from the sensor path stages. Basedon the calibration information, the monitoring device can thenintelligently adjust processing of the received sensor signal,accounting for the particular behavioral properties of the attachedcomponents.

Because monitoring systems according to such embodiments can adapt tothe specific properties of the attached components, these systems canprovide interchangeable use with a wide variety of components. Forexample, these systems can be used with components having a wide rangeof process and/or design characteristic variability.

Allowable manufacturing tolerances can be greatly expanded. Improvedmanufacturing repeatability and yields are achieved, as a result whilemaintaining a high degree of measurement accuracy.

The multi-stage calibration capability provides a generally fullyinterchangeable system in which existing components can be swapped outfor components of the same type or for components customized forparticular purposes. This type of mix and match capability providesenhanced ease of use and can also allow for the use of disposablecomponents, such as disposable sensor components. The use of disposablecomponents can provide a number of advantages including improvedsanitation and convenience.

For example, a user can select a sensor for use with a monitoring devicefrom a batch of sensors of the same type without verifying that theparticular sensor has been calibrated for use with that particularmonitoring device. The user can additionally combine this sensor withanother component, such as an instrument cable selected from a batch ofinstrument cables having the same type. Again, the user can attach thecable and sensor to the monitor and begin monitoring without verifyingthat the particular cable has been calibrated for use with thatparticular monitoring device or sensor.

In some cases, sensor path components can be initially characterized atthe factory, and the appropriate characterization information is storedon the component. The factory calibration can advantageously betransferred to the field as clinicians deploy the components withgenerally any compatible system without the need for independent fieldcalibration.

For example, in one scenario, a user first attaches a first sensor to afirst cable connected to a first monitoring device. The monitoringdevice reads the behavioral characteristics of the components andadjusts the signal processing parameters accordingly, such as when newsensor path components are attached. The user then replaces the firstsensor with a second sensor of the same type, but having differentbehavior characteristics, such as process variable characteristics. Inanother scenario, the user replaces the first sensor with a secondsensor having a different type, such as a sensor tailored for aparticular use, and having different design variable characteristics. Inboth scenarios, the monitoring device reads the behavioralcharacteristics of the second sensor and again performs multi-stagecalibration so as to cooperate with the second sensor.

The multi-stage calibration techniques described herein can benefitphysiological monitoring systems incorporating generally any type ofsensor. Additionally, in part because dynamic calibration allows forimproved manufacturing tolerance, they can be of particular benefit tosystems which measure relatively small signals, such as those includingacoustic sensors for measuring respiratory rate, heart sounds, and thelike.

Further embodiments of monitoring systems capable of multi-stagecalibration techniques are described below with respect to FIGS. 1through 6, for example.

Turning to FIG. 1, an embodiment of a physiological monitoring system100 for monitoring a medical patient is shown. The physiologicalmonitoring system 100 can be configured to implement the multi-stagecalibration techniques described herein, and includes a physiologicalmonitor 110 coupled with a sensor assembly 150 through a cable 130. Themonitor 110 includes various visual indicia and user controls 105 fordisplaying sensor parameters, alarms, and the like and for receivinguser input. The sensor assembly 150 could include any of a variety ofphysiological sensors. For example, the sensor assembly 150 couldinclude one or more optical sensors that allow the measurement of bloodconstituents and related parameters, acoustic respiratory sensors,electrocardiograph sensors, and the like.

More generally, the sensor assembly 150 can include one or more sensorsthat measure one or more of a variety of physiological parameters,including oxygen saturation, carboxyhemologbin (HbCO), methemoglobin(HBMet), fractional oxygen, total hemoglobin (HbT/SpHb), pulse rate,perfusion index, electrical heart activity via electrocardiography, andblood pressure. Other examples of physiological parameters that may bemeasured include respiratory rate, inspiratory time, expiratory time,inspiration-to-expiration ratio, inspiratory flow, expiratory flow,tidal volume, end-tidal CO₂ (ETCO₂), CO₂, minute volume, apnea duration,breath sounds, rales, rhonchi, stridor, changes in breath sounds such asdecreased volume or change in airflow, heart rate, heart sounds (e.g.,S1, S2, S3, S4, and murmurs), and changes in heart sounds such as normalto murmur or split heart sounds indicating fluid overload.

In some embodiments, the sensor assembly 150 can be an optical sensorhaving one or more emitters, such as light emitting diodes. The emittersmay emit multiple wavelengths of light that impinge on body tissue of aliving patient, such as a finger, foot, ear, or the like. The emittersmay also emit non-visible radiation. The sensor assembly 150 may furtherinclude one or more detectors that can receive light attenuated by thebody tissue of the patient. The detectors can generate physiologicalsignals responsive to the detected light. The sensor assembly 150 canprovide these physiological signals to the monitor 110 for processing todetermine one or more physiological parameters, such as certain of theparameters described above. An example of such a sensor assembly 150 isdescribed in U.S. Publication No. 2006/0211924, filed Mar. 1, 2006,titled “Multiple Wavelength Sensor Emitters,” the disclosure of which ishereby incorporated by reference in its entirety.

The cable 130 is connected to the sensor assembly 150 and to the monitor110. In some embodiments, the cable 130 includes two or more cables orcable assemblies, although it should be noted that the cable 130 canalso be a single cable 130. In the illustrated embodiment, the cable 130includes a sensor cable 112 and an instrument cable 114. The sensorcable 114 is connected directly to the sensor assembly 150 throughconnectors 133, 151, and the instrument cable 114 is connected directlyto the monitor 110 through a connector 131. The sensor cable 112 isconnected to the instrument cable 114 through connectors 135, 137.

In certain embodiments, the sensor cable 112 is a lightweight, flexiblecable used for a single medical patient and disposed of after use withthat patient. In contrast, the instrument cable 112 of certainembodiments is used for multiple patients and may be more durable thanthe sensor cable 112. For example, the instrument cable 112 may bethicker, stiffer, or heavier than the sensor cable 112. Advantageously,in certain embodiments, the lightweight, flexible characteristics of thesensor cable 112 make the sensor cable 112 more comfortable to attach toa patient. A patient with a sensor assembly 150 attached to her finger,for instance, could more easily move her hand with a lightweight sensorcable 112 attached to the sensor assembly 150. However, if some or allof the cable 130 were lightweight and flexible, it might be lessdurable. Hence, a portion of the cable 130 (e.g., the instrument cable114) is stronger and more durable, yet potentially heavier and lessflexible. The instrument cable 114 could therefore be used for multiplepatients, while the sensor cable 112 might be used for fewer patients,such as a single patient.

While the physiological monitor 110 of FIG. 1 is shown connecting to asingle sensor assembly 150, it may be advantageous in certainembodiments to connect to multiple sensors, such as sensors that monitordifferent physiological parameters. For instance, the physiologicalmonitor 110 could connect to a pulse oximetry sensor and an acousticsensor that measures respiratory rate, heart sounds, and relatedparameters. One way to provide multiple sensor functionality to thephysiological monitor 110 is to provide a splitter cable between themonitor and the cable 130 (see FIGS. 7 and 11). A splitter cable reducesor eliminates a need to build a second cable port into the chassis ofthe physiological monitor 110 to accommodate a second cable 130.Consequently, using a splitter cable can reduce costs. Moreover, using asplitter cable can reduce cross-talk noise between signal lines from thesensors.

However, as described above, upgrading the physiological monitor 110 toreceive input from multiple sensors using a splitter cable or the likecan create electrical shock hazards to the patient due to thepossibility of conductive paths forming through the sensors, cabling,and the patient. For example, if an acoustic sensor is placed on thechest and a defibrillator paddle touches the acoustic sensor, a surge ofcurrent could discharge through a conductive path formed in the patientbetween the acoustic sensor and a second sensor, and through thephysiological monitor 110. This current surge could injure the patientand damage the monitor 110.

Consequently, various embodiments of the cable 130 or an attachedsplitter cable can include one or more decoupling circuits (not shown)for reducing the risk of electric shock to the patient. Each decouplingcircuit can electrically decouple the sensor assembly 150 from themonitor 110 or can decouple multiple sensor assemblies 150. In additionto having its ordinary meaning, electrical decoupling can mean breakinga conductive path (e.g., by providing a dielectric between twoconductors) or increasing the resistance between conductors. Electricaldecoupling can be accomplished using transformers and/or optocouplers,as described below. The electrical decoupling of the decoupling circuitcan prevent or reduce harmful current surges from harming the patient.Example decoupling circuits compatible with certain embodiments areprovided below with respect to FIGS. 7 through 11.

In addition to including decoupling circuitry in the cable 130 or in anattached splitter cable, it may be desirable to include other circuitryin the cable 130 or splitter cable. For example, the cable 130, asplitter cable, and/or the sensor assembly 150 may include one or moreinformation elements (not shown), which can be memory devices such asEEPROMs or the like. The information elements may further storecalibration information related to one or more of the components in thesystem. The monitoring device may use such calibration information tocalibrate a multi-stage sensor path according to embodiments describedherein. Example compatible information elements are described below withrespect to FIGS. 3 through 6 and 11 through 17. In some embodiments, theinformation element stores other information such as cable managementinformation, patient context information, and/or physiologicalinformation.

FIG. 2 illustrates an embodiment of another sensor system capable ofincorporating certain multi-stage calibration techniques describedherein. The sensor system includes a sensor assembly 201, an instrumentcable 211, and a hub 220 suitable for use with any of the physiologicalmonitors and cables described herein. The sensor assembly 201 includes asensor 215, a cable assembly 217, and a first connector 205, while thecable assembly 217 of one embodiment includes a sensor cable 207 and apatient anchor 203.

The sensor assembly 201 is removably attachable to the instrument cable211 via the matable first and second connectors 205, 209. In turn, theinstrument cable 211 can be attached to a cable hub 220, which includesa port 221 for receiving a connector 212 of the instrument cable 211 anda second port 223 for receiving another cable. The hub 220 is an exampleof the splitter cable described above, and as such, can includedecoupling circuitry (see, e.g., FIG. 19). In certain embodiments, thesecond port 223 can receive a cable connected to an optical sensor(e.g., pulse oximeter) or other sensor. In addition, the cable hub 220could include additional ports in other embodiments for receivingadditional cables. The example hub 220 includes a cable 222 whichterminates in a connector 224 adapted to connect to a physiologicalmonitor (not shown).

In an embodiment, the acoustic sensor assembly 201 includes a sensingelement, such as, for example, a piezoelectric device or other acousticsensing device. The sensing element can generate a voltage that isresponsive to vibrations generated by the patient, and the sensor caninclude circuitry to transmit the voltage generated by the sensingelement to a processor for processing. In an embodiment, the acousticsensor assembly 201 includes circuitry for detecting and transmittinginformation related to biological sounds to a physiological monitor.These biological sounds can include heart, breathing, and/or digestivesystem sounds, in addition to many other physiological phenomena. Theacoustic sensor 215 in certain embodiments is a biological sound sensor,such as the sensors described or incorporated by reference herein. Insome embodiments, the biological sound sensor is one of the sensors suchas those described in U.S. patent application Ser. No. 12/044,883, filedMar. 7, 2008, entitled “Systems and Methods for Determining aPhysiological Condition Using an Acoustic Monitor,” (hereinafterreferred to as “the '883 application”), the disclosure of which ishereby incorporated by reference in its entirety. In other embodiments,the acoustic sensor 215 is a biological sound sensor such as thosedescribed in U.S. Pat. No. 6,661,161, which is incorporated by referenceherein in its entirety. Other embodiments include other suitableacoustic sensors.

The attachment mechanism 204 in certain embodiments includes first andsecond portions 206, 208 which can include adhesive (e.g., in someembodiments, tape, glue, a suction device, etc.). The adhesive can beused to secure the sensor 215 to a patient's skin. Moreover, one or morebiasing members 210 included in the first and/or second portions 206,208 can beneficially bias the sensor subassembly 202 in tension againstthe patient's skin and reduce stress on the connection between thepatient adhesive and the skin. A removable backing can be provided withthe patient adhesive to protect the adhesive surface prior to affixingto a patient's skin.

The sensor cable 207 can be electrically coupled to the sensorsubassembly 202 via a printed circuit board (“PCB”) (not shown) in thesensor subassembly 202. Through this contact, electrical signals arecommunicated from the multi-parameter sensor subassembly to thephysiological monitor through the sensor cable 207 and the cable 211.

In various embodiments, not all of the components illustrated in FIG. 2are included in the sensor system 200. For example, in variousembodiments, one or more of the patient anchor 203 and the attachmentsubassembly 204 are not included. In one embodiment, for example, abandage or tape is used instead of the attachment subassembly 204 toattach the sensor subassembly 202 to the measurement site. Moreover,such bandages or tapes can be a variety of different shapes includinggenerally elongate, circular and oval, for example. In addition, thecable hub 220 need not be included in certain embodiments. For example,multiple cables from different sensors could connect to a monitordirectly without using the cable hub 220.

Additional information relating to acoustic sensors compatible withembodiments described herein, including other embodiments of interfaceswith the physiological monitor are included in applications incorporatedby reference herein, such as the '883 application, for example.

FIGS. 3A and 3B illustrate example layouts of a physiological monitoringsystems 300A, 300B. FIGS. 3A and 3B illustrate various informationelements 360, 362, and 364. In certain embodiments, the physiologicalmonitoring systems 300 of FIGS. 3A and 3B implement multi-stagecalibration. For example, the information elements 360, 362, and 364 canstore calibration information usable to perform multi-stage calibrationin accordance with embodiments described herein. The informationelements 360, 362, 364 may additionally include other types ofinformation (e.g., cable management, patient context, and/orphysiological information). Although not shown, the information elements360, 362, and 364 may also be included in any of the splitter cablesdescribed herein. Moreover, decoupling circuitry may be included in thecables of FIGS. 3A and 3B.

Referring to FIG. 3A, a physiological monitoring system 300A includes aphysiological monitor 310 that communicates with a sensor 350 through aninstrument cable 314 and a sensor cable 312. An information element 360is included in the sensor cable 312.

The physiological monitor 310 interfaces with the instrument cable 314using a connector 319, which mates with a connector 331 of theinstrument cable 314. The instrument cable 314 mates in turn with thesensor cable 312 through a connector 335 on the instrument cable 314 anda corresponding connector 337 on the sensor cable 312. The sensor cable312 in turn connects to a sensor 350 through a connector 333 and acorresponding connector 351 on the sensor 350. In alternativeembodiments, the sensor cable 312 may be a splitter cable.

In the embodiment shown, the information element 360 is located in theconnector 337. Other placements for the information element 360 are alsopossible. For example, the information element 360 could be locatedanywhere in the sensor 350 or in the sensor cable 312, including in asensor cable section 332 or the connector 333. In addition, theinformation element 360 could also be located in the instrument cable314 instead, or two or more information elements 360 could be used, oneor more in each cable 312, 314 (see, e.g., FIG. 3).

The information element 360 can include any one or more of a widevariety of types of information elements. In an embodiment, theinformation element 360 is a non-volatile information element, such as,for example, an erasable programmable read-only memory (“EPROM”).“EPROM” as used herein includes its broad ordinary meaning known to oneof skill in the art, including those devices commonly referred to as“EEPROM “EPROM,” as well as any types of electronic devices capable ofretaining their contents even when no power is applied and/or thosetypes of devices that are reprogrammable. In an embodiment, theinformation element is an impedance value associated with the sensor,such as, for example, a resistive value, an impedance value, aninductive value, and/or a capacitive value or a combination of theforegoing. In addition, the cable's information element could beprovided through an active circuit such as a transistor network, memorychip, flash device, or other identification device, includingmulti-contact single wire information elements or other devices, such asthose commercially available from Dallas Semiconductor or the like.Moreover, the information element may be random access memory (RAM),read-only memory (ROM), or a combination of the same.

In an embodiment, the physiological monitor 310 communicates with theinformation element 360 via a serial transmission line 340. In oneembodiment, the serial transmission line 340 is a multi-drop bus,although in alternative embodiments, the serial transmission line 340 isa 1-wire bus, a SCSI bus, or another form of bus. Once the physiologicalmonitor 310 determines that it is connected to the sensor cable 312, itsends and receives signals to and from the information element 360 toaccess calibration information, cable management information and/orpatient context information. Alternatively, the physiological monitor310 does not access the information element 360 until requested to do soby a user (e.g., a clinician). In addition, the physiological monitor310 may also automatically access the information element 360 or accessthe information element 360 in response to a user request.

FIG. 3B illustrates another embodiment of a monitoring system 300B. Themonitoring system 300B preferably includes all the features of themonitoring system 300A and additionally includes an information element362 in the instrument cable 314 and an information element 364 in thesensor 350. The information elements 362, 364 may have the same ordifferent characteristics of the information element 360, including thesame or different memory type, capacity, latency, or throughput.

In an embodiment, the serial transmission line 340 connects thephysiological monitor 310 to the information element 360 in the sensorcable 312 as above. However, the serial transmission line 340 alsoconnects to the information elements 362, 364. The physiological monitor310 may therefore access the information elements 360, 362, 364 whilerunning generally few transmission lines 340.

The information elements 362, 364 may have all or a portion of thefunctionality of the information element 360. In one embodiment, thesame data is stored in each of the information elements 360, 362, 364,thereby providing data redundancy. Additionally, in such embodiments theinstrument cable 314 may stay with the patient as the patient moves fromone department to another, in place of or in addition to the sensorcable 312. Moreover, in one embodiment only the instrument cable 314 orthe sensor assembly 350 has an information element 362 or 364, and thesensor cable 312 does not have an information element 360.

The placement of the information elements 362, 364 can be in any of avariety of locations. For example, the information element 362 may belocated in either one or the connectors 331, 335 or in the instrumentcable section 334. Likewise, the information element 364 of the sensor350 may be located in the connector 351 or in another part of the sensor350.

Although not shown, the sensor cable 312 and/or the instrument cable 314may have multiple information elements in some embodiments. Whenmultiple information elements are used, certain data may be stored onsome information elements, and other data may be stored on others. Forinstance, calibration, cable management information, patient contextinformation, physiological information, etc., or any combination thereofmay be stored separate information elements.

Referring to FIG. 3B for the purposes of illustration, each of thecomponents in the sensor path, including, for example, the sensor 350,the sensor cable 314 and the instrument cable 312 form one or morestages. Additionally, each stage can have a respective informationelement 364, 360, 362 associated with it.

One or more additional stages may be located in the monitor 310. Forexample, The monitor 310 can further include one or more components(e.g., front-end processing circuitry) and one or more informationelements (not shown) storing calibration information related to thosecomponents. Example front end processing circuitry is described belowwith respect to FIG. 5. Further additional stages may be included, orone or more of the stages shown in FIG. 3B may not be included incertain embodiments.

The instrument cable 314 may include a splitter cable such as any of thesplitter cables described herein. Additionally, in some embodiments, thesensor includes an integrated cable which connects to the sensor cable312. Such a configuration is shown in FIG. 2, discussed above. Forexample, referring to FIG. 2, information elements storing calibrationinformation may be included on one or more of the sensor assembly 201,the monitor cable 211 and the hub 220.

The monitor 310 includes at least one processor (not shown) such as anyof those described herein which receives the signal detected by thesensor after it has gone through each of the stages. Thus, the signal orsignals received by the processor has been modified according to thecharacteristic responses of each of the stages. The processor performssignal processing on the received signal to extract signalsrepresentative of one or more physiological parameters, such as any ofthe parameters described herein (e.g., respiratory rate, SpO₂, etc.).

In certain embodiments, the system 300B is further configured forcalibration of the multi-stage signal path. The information elementsstore calibration information related to behavioral characteristics ofone or more of the stages such as the sensor 350, the sensor cable 312,the instrument cable 314, and/or front-end processing circuitry in themonitor. Using the calibration information, the monitor 310 isconfigured to adjust the processing of the received signal or signals soas to account for the specific behavioral characteristics of the stages.Thus, the system dynamically accesses predetermined response informationrelated to the attached components and can produce accurate measurementsgenerally regardless of the variable characteristics of thosecomponents.

For example, in some embodiments the calibration information from eachinformation element corresponds to a characteristic response of acorresponding stage or portions of that stage. Alternatively, thecalibration information may not be directly representative of theresponse and the processor instead derives the response from thecalibration information.

In some embodiments, the processor performs the inverse of the responseof one or more of the stages to calibrate the system, although othersuitable computations can be employed. In some embodiments, theprocessor determines a transfer function associated with one or more ofthe stages or portions thereof and performs the inverse transferfunction to reconstruct the signal.

A multi-stage calibration module running on the processor may performthe calibration process, for example. The calibration module in someembodiments operates on the signal received from the final stage in thesignal path before other signal processing is performed on the signal.In another embodiment, the multi-stage calibration is performedsubstantially in parallel with other signal processing. In oneembodiment, the calibration module reconstructs the original sensorsignal. For example, the calibration module generates a signalsubstantially representative of the voltage or current signal output bythe sensor, removing the effects of the other components in the sensorpath.

In one embodiment, rather than computing and compensating for theresponse of each stage individually, the processor uses the calibrationinformation from all of the stages to determine a single combinedmulti-stage response. The processor can then automatically calibrate thesignal processing algorithm based on the combined response, such as byperforming the inverse of the combined response or by performing someother suitable computation.

In certain embodiments, one or more of the systems 300A, 300B of FIGS.3A and 3B are configured to calibrate the processing of the sensorsignal in response to calibration information stored on one or more ofthe information elements 362, 360, 364 and/or one or more otherinformation elements in the sensor path.

In some embodiments, the system 300B may be capable of performingtargeted noise compensation by reducing the effect of noisy componentsin the signal path. For example, the system of some embodimentsidentifies certain components or portions thereof which are contributinga relatively high amount of noise and adjusts the processing of thesensor signal accordingly. For example, the system 300B may identifyand/or compensate for relatively high noise stages by manipulating theresponses (e.g., transfer functions) associated with the correspondingstages during signal processing. One or more of the components can haveprogrammable operating values, and the system may adjust one or more ofthose programmable values to identify and/or compensate for relativelyhigh noisy stages.

As described, other types of information in addition to calibrationinformation can be stored on one or more of the information elements.For example, cable management information that may be stored on theinformation element 360 may include information on cable usage, sensorusage, and/or monitor usage. Cable usage data may include, for example,information on the time the cable has been in use, enabling thephysiological monitor 310 to determine when the sensor cable 312 is nearthe end of its life. Sensor usage data may include, for example,information on what sensors have been attached to the sensor cable 312,for how long, and the like. Similarly, monitor usage data may include,for example, information on what monitors have been attached to thesensor cable 312, for how long, and the like. More detailed examples ofcable management information are described below, with respect to FIG.4.

Patient context information that may be stored on the informationelement 360 may include patient identification data and patient flowdata. In one example embodiment, patient identification data includes atleast the patient's name and one or more identification numbers. Patientflow data may include, for example, details regarding the departmentsthe patient has stayed in, the length of time therein, and devicesconnected to the patient. More detailed examples of patient contextinformation may also be found below, with respect to FIG. 4.

Advantageously, in certain embodiments, the physiological monitor 310uses the cable management information in various embodiments todetermine when to replace a cable in order to prevent cable failure. Thephysiological monitor 310 may also use the information element 360 totrack sensor 350 and physiological monitor 310 use. Some implementationsof the physiological monitor 310 enable the physiological monitor 310 totransmit some or all of the cable management information to a centralnurses' station or to a clinician's end user device, such as isdescribed in further detail with respect to FIG. 4. In someimplementations, the physiological monitor 310 or a central nurses'station sends an alarm to the end user device that alerts the user toimpending cable failure. For example, a clinician might receive an alarmnotification on a personal digital assistant (PDA), pager, or the like,which enables the clinician to replace the cable before it fails.Patient context information, including identification information, mayalso be provided along with the alarm to help the clinician identify thecable with the patient.

Moreover, the physiological monitor 310 may transmit some or all of thecable management information and/or patient context information to acentral server (see, e.g., FIG. 13). Inventory software on the centralserver can use this information to preemptively order new cables whencable inventory is low or at other times.

Different sensors 350 and physiological monitors 310 may be attached tothe same sensor cable 312. Thus, the cable management information mayalso include a list of which sensors 350 and physiological monitors 310have been attached to the cable 312, how long they were attached, andthe like. The physiological monitor 310 may also provide thisinformation to the central server to keep track of or journal thisinformation. The cable management information is therefore used in someembodiments to derive patient monitoring metrics, which may be analyzedto monitor or improve hospital operations. A hospital may use thesemetrics, for example, to determine when to replace cables or todetermine whether personnel are using the cables improperly or aredamaging the cables through improper use.

The patient context information in some embodiments also enables thesensor cable 312 to be identified with a particular patient. As thesensor cable 312 of some embodiments may be transported with the patientwhen the patient is moved about the hospital, when the sensor cable 312is attached to different monitors 350, the data stored in theinformation element 360 may be transferred to the new monitor 350. Thus,during the patient's stay at the hospital or at discharge, theinformation element 360 of certain embodiments has patient flow datathat a hospital can use to monitor or improve operations. The flow dataof multiple patients may be used, for instance, to determine the numberof patients staying in a particular department at a given time and theequipment used during those patients' stay. Knowing this information,the hospital can adjust equipment inventories and staff assignments tomore efficiently allocate hospital resources among the variousdepartments.

FIG. 3C illustrates an embodiment of a circuit 300C for facilitatingcommunication between a monitor and one or more information elements390. The circuit 300C may be included in any of the cable or sensorassemblies described above, including in a splitter cable, anon-splitter cable, an instrument cable, a sensor cable, a sensorassembly, combinations of the same, and the like. In addition, thecircuit 300C may be used in conjunction with the circuits 500B and 500Cin a single cable, e.g., on the same circuit board, or in combinationwith multiple cables and/or sensor assemblies.

Advantageously, in certain embodiments, the circuit 300C provideselectrical decoupling for communications lines 377, 379, 382, and 383,which provide communications between a monitor and one or moreinformation elements. In addition, the circuit 300C may provide sensorconnection status to a monitor via a sensor detect circuit 372.

A decoupling circuit 540 d shown includes digital decoupling logic toelectrically decouple one or more information elements and one or moresensors from the monitor. The decoupling circuit 540 d includestransformers on a chip and associated logic that perform digitaldecoupling. In one embodiment, the decoupling circuit 540 d is aADuM130x series chip from Analog Devices. In other embodiments,optocouplers and/or other transformers are used.

Communications lines 382, 383 allow the monitor to transmit and receivedata to and from one or more information elements 390. The line 382 is amonitor transmit line 382, and the line 383 is a monitor receive line383. Each of these lines 382, 383 is electrically decoupled from thecommunications line 377 by the decoupling circuit 540 d. Thecommunication lines 377, 379 may be electrically coupled with the one ormore information elements 390.

In an embodiment, the communications line 377 is a bus, such as a 1-wirebus. The communications line 377 may be used to both transmit andreceive data to and from the monitor. The communications line 379 may beused to receive data from the monitor. A MOSFET switch 376 or the likeis in communication with the depicted communications line 379, whichselectively transmits signals to the one or more information elements390.

The monitor receive line 383 is in communication with a power validationcircuit 378, which determines whether the feedback power VFB describedabove with respect to FIG. 3C is high enough. If the feedback power VFBis too low, the data received from the information elements 390 may notbe used because the data may be corrupt.

In the depicted embodiment, the power validation circuit 378 includes acomparator 389 that compares the feedback power VFB with a referencevoltage. If the feedback power VFB is equal to or higher than thereference voltage, the comparator 389 might output a high voltage. Thishigh voltage can be selectively overridden by a MOSFET switch 387 inresponse to communications received from the information elements 390.If the feedback power VFB is lower than the reference voltage, thecomparator 389 might output a low voltage. The low voltage can overridethe MOSFET switch 387 such that communications from the informationelements 390 are not sent to the monitor.

In the depicted embodiment, sensor connection status is provided to themonitor via the sensor detect circuit 372. The sensor detect circuit 372includes a sensor detect line 375 in communication with a pull-upresistor 373. When a sensor 385 is not connected to the line 375, theline 375 may be pulled high. This high voltage may be inverted by aMOSFET switch 374 to provide a low signal to the monitor via sensorconnect line 381. The switch 374 may be omitted in some embodiments.

In response to a sensor 385 being connected to the sensor detect line375, a shorted line 386 (or low resistance line) in the sensor 385 cancause the line 375 to be pulled low. This low value can be inverted bythe switch 374 to provide a high signal to the monitor. This signal canindicate that the sensor 385 is connected. Conversely, if the sensor 385is disconnected, the line 375 may again be pulled high, resulting in alow output of the switch 374. As a result, the monitor may receive arapid or near-immediate indication that the sensor 385 has beendisconnected.

The sensor detect circuit 372 also includes passive elements in thedepicted embodiment, such as a capacitor 391, to smooth or debouncecontact oscillations from the sensor 385. Thus, the sensor detectcircuit 372 can also be considered a debounce circuit. In otherembodiments, the sensor detect circuit 372 can be replaced with otherforms of debounce circuitry.

Advantageously, in certain embodiments, the sensor detect circuit 372can be used instead of polling the one or more information elements 390frequently to determine if the sensor 385 is connected. Alternatively,the polling cycle of the one or more information elements 390 may bereduced. Reducing or eliminating the polling cycle can reduce powerconsumption by the circuit 300C.

The sensor detect circuit 372 may be used to detect the connection ofcables, such as a splitter cable, as well as or instead of detectingsensor connections. In some embodiments, a sensor detect line 375 may beprovided for each sensor in a multi-sensor system, each cable, or thelike. Moreover, the sensor detect circuit 372 may also be used withcables that do not have a decoupling circuit.

FIG. 4 illustrates a block diagram of example forms of data that can bestored on an information element 460. In the depicted embodiment,patient context information 420, cable management information 430,physiological information 440 and calibration information 450 are shown.The patient context information can include patient identification data422 and patient flow data 424. Cable management information 430 caninclude cable usage data 432, sensor usage data 434, and instrumentusage data 436. However, while the data is depicted in FIG. 4 ascomprising discrete categories, data from one category may be includedwithin another. Data from one or more categories also may not beincluded, or alternatively, additional data categories than that shownmay be included.

The calibration information 450 may be related to the characteristics ofthe components attached to the system. For example, each informationelement may store information related to behavioral characteristics ofthe corresponding component (e.g., a sensor or cable) to which it isattached.

Such information can include electrical properties such as capacitances,impedances, resistances, and the like. The information element 460 mayfurther store mechanical properties such as a mechanical sensitivity ofa sensing element. For example, in an embodiment, an acoustic sensorassembly includes a piezoelectric membrane that vibrates in response tomechanical vibrations generated by the physiological sounds of apatient. The membrane generates a corresponding voltage signal. Themechanical sensitivity of such a device, or the mechanical properties ofother mechanical components can be stored in the information element460.

Additionally, frequency response characteristics such as cut-in andcut-off values can be stored. These cut-in and cut-off values can bemechanical values, such as for a piezoelectric membrane of an acousticsensor, or electrical cut-in and cut-off values, such as for one or morecircuit components. In addition to having their ordinary meaning,mechanical cut-in and cut-off frequencies may correspond to the lowestand highest frequency values, respectively, at which a particularcomponent passes a signal from its input to its output. Saturationvalues and/or gain characteristics of certain components (e.g., circuitcomponents) may also be included.

In addition to these specific examples and categories of calibrationinformation, a wide variety of other calibration data may be used.Generally, any data related to characteristics of components in thesensor path may be stored.

In one embodiment patient identification data 422 can include apatient's name, a patient's unique hospital identification number, typeof patient or body tissue, information about the patient's age, sex,medications, and medical history, and other information that can beuseful for the accuracy of alarm settings and sensitivities and thelike. In addition, the patient identification data 422 may also includean SpO₂ fingerprint, determined by a pulse oximeter. In one suchembodiment, the SpO₂ fingerprint is determined by calculating a ratio ofan infrared detected wavelength and a red detected wavelength. The SpO₂fingerprint can be used to detect if a sensor or cable is beingimproperly reused.

Patient flow data 424 can include a record of departments the patienthas visited, length of stay (LOS) in those departments, overall LOS inthe hospital, admittance date and time, discharge date and time, timestamps for events occurring in the hospital, and the like. Some or allof this information, in conjunction with the patient identificationdata, can constitute a patient flow profile.

Cable usage data 432 may include buyer or manufacturer information,cable type, serial number of the cable, date of purchase, time in use,and cable life monitoring functions (CLM), including near expirationpercentage, update period, expiration limit, and an index of functions.In addition, the cable usage data 432 may include numerous read writeparameters, such as the number of times the cable is connected to amonitoring system, the number of times the cable has been successfullycalibrated, the total elapsed time connected to a monitor system, thenumber of times the cable has been connected to one or more sensors, thetotal time used to process patient vital parameters, the cumulativecurrent, voltage, or power applied to the cable, the cumulativetemperature of the cable, and the expiration status of the cable.

In an embodiment, the number of times the cable is placed on or removedfrom a patient is monitored and an indication is stored in the memory.The number of times a sensor connected to the cable is placed on orremoved from a patient can be monitored by monitoring the number ofprobe off conditions sensed, or it can be monitored by placing aseparate monitoring device on the cable or sensor to determine when asensor clip is depressed, opened, removed, replaced, attached, or thelike.

In an embodiment, the average operating temperature of the cable ismonitored and an indication stored. This can be done, for example,through the use of bulk mass or through directly monitoring thetemperature of the cable or the temperature of the cable's connectors.In an embodiment, the number of different monitors connected to thecable is tracked and an indication is stored in memory. In anembodiment, the number of times the cable is calibrated is monitored,and an indication is stored in memory. In an embodiment, the number ofpatients that use a cable is monitored and an indication is stored. Thiscan be done by, for example, by storing sensed or manually enteredinformation about the patient and comparing the information to newinformation obtained when the cable is powered up, disconnected and/orreconnected, or at other significant events or periodically to determineif the cable is connected to the same patient or a new patient. In anembodiment, a user is requested to enter information about the patientthat is then stored in memory and used to determine the useful cablelife. In an embodiment, a user is requested to enter information aboutcleaning and sterilization of the cable, and an indication is stored inthe memory. Although described with respect to measuring certainparameters in certain ways, various other electrical or mechanicalmeasurements can be used to determine any useful parameter in measuringthe useful life of a cable.

Sensor usage data 434 can include some or all of the same information asthe cable usage data but applied to sensors attached to the cable, andmay also include information on the type or operation of the sensor,type or identification of a sensor buyer, sensor manufacturerinformation, sensor characteristics including the number of wavelengthscapable of being emitted, emitter specifications, emitter driverequirements, demodulation data, calculation mode data, calibrationdata, software such as scripts, executable code, or the like, sensorelectronic elements, sensor life data indicating whether some or allsensor components have expired and should be replaced, encryptioninformation, monitor or algorithm upgrade instructions or data, or thelike. In an embodiment, the sensor usage data 434 can also includeemitter wavelength correction data.

Sensor usage data 434 can also include the number of emitting devices,the number of emission wavelengths, data relating to emission centroids,data relating to a change in emission characteristics based on varyingtemperature, history of the sensor temperature, current, or voltage,emitter specifications, emitter drive requirements, demodulation data,calculation mode data, the parameters it is intended to measure (e.g.,HbCO, HbMet, etc.) calibration data, software such as scripts,executable code, or the like, sensor electronic elements, whether it isa disposable, reusable, or multi-site partially reusable, partiallydisposable sensor, whether it is an adhesive or non-adhesive sensor,whether it is reflectance or transmittance sensor, whether it is afinger, hand, foot, forehead, or ear sensor, whether it is a stereosensor or a two-headed sensor, sensor life data indicating whether someor all sensor components have expired and should be replaced, encryptioninformation, keys, indexes to keys or has functions, or the like monitoror algorithm upgrade instructions or data, and some or all of parameterequations.

Instrument usage data 436 can include buyer or manufacturer information,information on the type of monitors that the cable has connected to,number of monitors the cable has connected to, duration of cableconnections to the monitors, duration of use of the monitor, trendhistory, alarm history, sensor life, an identification number for aspecific monitor, and the like. In addition, the instrument usage data436 may include all or a portion of all the cable and sensor usage datadescribed above.

The physiological information 440 may include any of the physiologicalparameters described above, obtained from the sensors or monitorsattached to the information element 460. In one implementation, theinformation element 460 enables the physiological information 440 to betransferred between physiological monitors. As a result, a historicalview of the patient's physiological parameters may be provided todifferent monitors throughout the hospital. Thus, clinicians indifferent departments can observe the patient's physiologicalinformation obtained in a previous department, enabling clinicians toprovide a higher quality of care.

FIG. 5 illustrates a functional block diagram of an acoustic signalprocessing system 500. The block diagram illustrates components whichmay be included on portions of various stages of a monitoring systemhaving a multi-stage sensor path, for example. The processing system 500includes an acoustic sensor 502 which can detect a physiological signaland produces a corresponding voltage signal. In one embodiment, thesensor 502 is an acoustic sensor such as one of the acoustic sensorsdescribed herein and is configured to measure at least one of apatient's respiratory rate, heart sounds, and related parameters.

The system 500 further includes front end circuitry 504 configured tocondition the analog electrical signal output by the sensor 502 forprocessing. The front end circuitry 504 includes a pre-amplificationcircuit 506, one or more filters 508, a high gain stage 510, a low gainstage 512, and an analog to digital converter (ADC) 514. The system 500further includes a digital signal processor (DSP) and a display 518.

The preamplification circuit 506 receives and amplifies the voltagesignal from the sensor, such as by a predetermined gain. The one or morefilters 508 modify the preamplified signal by, for example, smoothing orflattening the signal. In one embodiment, the one or more filters 508include a high pass filter which passes high frequency signals andattenuates low frequency signals. The one or more filters 508 mayinclude other types of filters, such as low pass or bandpass filters maybe used instead of, or in addition to a high pass filter in someembodiments.

The output from the filter 508 is divided into two channels, forexample, first and second channels 520, 522. In some embodiments, morethan two channels may be used. For example, 3, 4, 8, 16, 32 or morechannels may be used. The voltage signal is transmitted on both firstand second channels 520, 522 to gain bank 509. The gain bank 509 incertain embodiments includes one or more gain stages. In the depictedembodiment, there are two gain stages 510, 512. A high gain stage 510amplifies the voltage signal into a higher voltage signal. A low gainstage 512 in certain embodiments does not amplify or attenuates thevoltage signal. In alternative embodiments, the low gain stage 512 mayamplify the voltage signal with a lower gain than the gain in the highgain stage 510.

The amplified signal at both first and second channels 520, 522 thenpasses to an analog-to-digital converter (ADC) 514. The ADC 514 has twoinput channels to receive the separate output of both the high gainstage 510 and the low gain stage 512. The ADC bank 514 samples andconverts analog voltage signals into digital signals. The digitalsignals then pass to the DSP 516 for processing. A display 518 thenoutputs a graphical display of one or more physiological parameters suchas a respiratory rate, heart sounds, etc., based on the processedsignal. In certain embodiments, a separate sampling module samples theanalog voltage signal and sends the sampled signal to the ADC 514 forconversion to digital form. Additionally, in certain embodiments twoADCs 514 may be used in place of one ADC 514.

A variety of configurations are possible for the processing system 500.For example, one or more of the illustrated components may not beincluded in certain embodiments. In other embodiments, additionalcomponents may be used instead of or in addition to the illustratedcomponents. Example compatible processing systems 500 are described inthe '883 application and are incorporated by reference herein.

Example Multi-Stage Calibration System Implementation

As discussed, the various components of the acoustic processing system500 may be dispersed throughout various stages of a monitoring systemhaving a multi-stage sensor path. An example implementation of amulti-stage monitoring system capable of performing an examplemulti-stage calibration process will now be described with reference toFIGS. 2, 3 and 5. The example system includes a sensor path arrangementcompatible with those depicted in FIGS. 2 and 3 implementing an acousticprocessing system such as the processing system 500 of FIG. 5. Thisexample implementation is provided for the purposes of illustration, andis not limiting.

Referring again to FIG. 2, the sensor assembly 201 including the sensor215 and integrated sensor cable 217 form a first stage in the exampleimplementation. The instrument cable 211 forms a second stage andincludes preamplification circuitry, such as the preamplificationcircuitry 506 of FIG. 5. By placing the preamplification circuit in acomponent other than the sensor, such as the instrument cable 211, costcan be reduced. For example, in one embodiment, a disposable sensor isused, or the sensor 215 otherwise requires more frequent replacementthan the reusable instrument cable 211. For example, the sensor 215 maybecome soiled or generally wear out more quickly than the instrumentcable 211, due to repeated contact with the patient, relatively morefragile componentry, etc. Thus, it is advantageous to reduce the costand complexity of constructing the sensor 215 by moving thepreamplification circuit to the instrument cable 211.

Additionally, in order to amplify the sensed signal for processingbefore significant attenuation or other signal degradation occurs, itcan be desirable to place the preamplification circuit generally asclose to the sensor as possible. Thus, in one embodiment, thepreamplification circuitry is located on the connector 209 of theinstrument cable 211, which is adjacent to the sensor assembly 201 in anattached configuration. Thus, the preamplification circuitry in thisembodiment is both relatively close to the sensor in the signal path andis on a separate component, achieving both performance benefit and costsavings. In other embodiments, the preamplification circuit resides onthe sensor 215 or at some other location.

The hub 220 forms a third stage, and a front end module in the monitor(not shown) forms a fourth stage and includes the components of thefront end circuitry other than the pre-amplification circuit. Forexample, the front end module includes one or more filters, high and lowgain stages, and an ADC such as those of the system 500 of FIG. 5. Inother embodiments, all of the front end circuitry is located in themonitor, some other stage, or is dispersed through the stages in someother manner. The monitor also houses a DSP and a display such as theDSP 516 and display 518 of FIG. 5.

Additionally, each of the four stages include at least one associatedinformation element. While the information elements may be located in avariety of locations, in the example embodiment the information elementsassociated with stages one through four are located on the connector 205of the integrated sensor cable 217, the connector 209 of the instrumentcable, within the housing of the hub 220, and in the monitor,respectively.

In the example implementation, the information element associated withthe example first (sensor) stage is a 1 Kbit EEPROM, although othertypes of information elements can be used. The information elementstores data relating to the mechanical sensitivity of the piezoelectricsensing element, one or more mechanical cut-in and cut-off frequencies,and one or more capacitances associated with the sensor 215. In oneembodiment, the mechanical sensitivity may be determined by comparingthe amplitude of an acoustic input signal to the amplitude of theresulting voltage signal. In addition to having its ordinary meaning,mechanical cut-in and cut-off frequencies may correspond to the lowestand highest frequency values, respectively, of physiological sounds thatthe sensor 215 is capable of detecting to produce a correspondingvoltage signal. The capacitance values may correspond to one or more ofthe output capacitance of the sensor 215, the capacitance of theintegrated sensor cable 217, a combination thereof, or some othercapacitance.

In one embodiment, the information element associated with the examplesecond (instrument cable/preamplifier) stage is a 1 Kbit EEPROM andincludes information relating to characteristics of the preamplifier 506such as one or more of a differential gain value, input impedance,cut-in and/or cut-off frequencies, a minimum saturation value, and thelike. In one embodiment, the cut-in frequency is not stored in theEEPROM but is instead computed (e.g., by the monitor) using thecapacitance of the first stage and the input impedance of the secondstage. Thus, by taking advantage of the information already stored inthe previous stage, less memory space is used. As a result, smallermemory components or less memory components may be used, providingpotential cost savings. In other embodiments, the cut-in frequency isstored on the information element.

The example third stage formed by the hub 220 includes a 20 Kbit EEPROMwhich stores information related to the hub 220. As discussed, the hub220 can include electrical decoupling circuitry. In the exampleembodiment, the hub 220 includes decoupling circuitry having anoptocoupler and/or transformer such as the decoupling circuitrydescribed herein with respect to the example hub 1720 of FIG. 17.

The decoupling circuitry may exhibit some amount of phase change and/ornon-linear behavior such as signal compression, for example. Informationis stored in the information element which can be used to account forthis behavior. For example, one or more coefficients are stored in theEEPROM which can be used to construct the curve of the non-linearresponse. Additional information related to the hub 220 is stored in theinformation element and can include, for example, a gain, cut-in andcut-off frequencies, output resistance, and minimum saturation level ofthe hub stage.

As discussed, the fourth stage in the example embodiment is located onthe monitor and includes the front end circuitry other thanpreamplifier, which is stored in the instrument cable 211. Theinformation element associated with the fourth stage can be a flashmemory, for example, and is configured to store calibration data relatedto the properties of the front end circuitry components. For example,such information can include gain and frequency cut-off values for thehigh gain channel, gain and cut-off frequency values for the low gainchannel, etc.

The fourth stage may also have a characteristic input gain value. In theexample embodiment, this value is not stored by the information elementbut is instead computed (e.g., by the monitor) using the outputresistance from the previous stage. Again, by taking advantage of storedinformation, less memory is used, providing cost savings. Alternatively,the input stage gain value may be stored on the information element.

A processor in the monitor downloads the calibration information fromthe information elements of the four stages and performs the multi-stagecalibration based on the information. For example, the processor mayacquire or generate a mathematical representation of the responses(e.g., transfer functions) associated with one or more of the stages orportions thereof. The processor may then perform an appropriatecomputation to generally remove or modify the effect of the four stagesor portions thereof on the sensor signal. For example, the processor mayperform the mathematical inverse (e.g., inverse transfer functions) ofthose responses. In general, any appropriate mathematical operationincorporating the calibration information may be used.

While a variety of types of calibration information have been describedwith respect to the above example embodiment, a wide variety of otherkinds of information (e.g., quality control information, compatibilityinformation, cable management information, patient context information,and/or physiological information, etc.) may be stored in otherconfigurations. Additionally, other or additional types of componentsincluding different information elements, front end circuitrycomponents, sensors, cables, etc., are contemplated. Moreover, while theexample implementation involves a system incorporating an acousticsensor, systems having other types of sensors (e.g., optical sensorssuch as pulse oximeter sensors) may also incorporate the multi-stagecalibration described herein.

In the example implementation, physically separable components generallyform separate stages. In other embodiments, stages may be delineated insome other manner, such as based on functionality rather than physicalseparability. Additionally, in some embodiments, one or more physicallyseparable components do not include calibration information and themonitor does not factor in characteristics associated with thatcomponent in the adaptive processing.

In certain embodiments the monitoring system is a “restricted access”system, which generally only functions with quality-controlledcomponents that are authorized or compatible, such as components orfamilies of components from a specific manufacturer or licensed vendor.This restricted access functionality can ensure proper functioning andquality of the monitoring system, for example, providing safetybenefits.

In such systems, each of the information elements may includeauthentication information indicating that the corresponding componentis compatible with the system. The authentication information mayinclude predetermined data such as a key or other information capable ofidentifying the respective component as a compatible with the system.

The monitoring device can be configured to read the authenticationinformation and verify that each of the attached components isauthorized or otherwise compatible with the system. If the componentsare compatible, the monitoring device enables physiological monitoring.On the other hand, if one or more of the components do not have theappropriate authentication information, the monitoring device disablesthe monitoring function. Such authentication information may be storedin combination with the calibration information discussed above.

In some embodiments, only select components in the system requireauthentication by the monitor. For example, in one embodiment, thesensor is the only device including authentication information.

Examples of restricted access technology compatible with embodimentsdescribed herein are provided in U.S. Pat. No. 7,843,729, titled “PulseOximeter Access Apparatus and Method,” the disclosure of which is herebyincorporated by reference in its entirety.

FIG. 6 illustrates a flowchart diagram of an example physiologicalmonitoring process 600 incorporating multi-stage calibration. In oneembodiment, the process 600 begins at step 602, where the process 600determines whether a compatible multi-stage sensor path is appropriatelyconnected to the monitor. The process 600 may enter step 602 when itreceives an indication that a user would like to begin physiologicalmonitoring, for example. In another embodiment, the process 600 mayenter step 602 when it detects that one or more components have beenconnected to the monitor.

At step 602, for example, the process 600 may electrically ping orotherwise communicate with the components in the sensor path (e.g.,sensors, cables, etc.) to determine whether a compatible sensor pathconfiguration is connected to the monitor. In one embodiment, theprocess 600 downloads and verifies quality control and/or authenticationinformation from each of the stages in the sensor path at step 602 todetermine if the sensor path configuration is compatible. Generally, anyof the types of information described herein can be advantageously usedin the compatibility determination (e.g., quality control information,cable management information, patient context information, and/orphysiological information). If one or more of the sensor path stages arenot compatible or are not appropriately connected, the process 600waits.

If the components of the multi-stage sensor path are appropriatelyconnected, the process 600 of some embodiments obtains calibrationinformation from information elements associated with one or more of thestages at step 604. For example, the process may download calibrationinformation from one or more of a sensor, instrument cable, splittercable, front-end circuitry, and/or some other component. In oneembodiment, the process 600 downloads the information from the attachedcomponents serially, such as in the order in which they are connected.In other embodiments, the process 600 may receive the information inparallel from one or more of the stages, or in another suitable manner.

The process 600 continues to step 606, where the process 600 adjusts oneor more signal processing parameters of the physiological monitor basedon the calibration information. For example, the process 600 determinesthe characteristic response associated with one or more of the stages orportions thereof using the calibration information. In some embodiments,the process 600 then adjusts one or more parameters of a signalprocessing algorithm using the determined responses or other calibrationinformation.

At step 608, the process 600 processes the detected signal according tothe adjusted processing parameters. For example, the process 600 mayperform multi-stage calibration by applying the inverse of one or moreof the calculated sensor path stage responses as described herein, or byperforming some other compatible operation. In general, any of theautomatic calibration techniques described herein may be used, such asthose described with respect to FIG. 2, 3B, or 5, for example. In otherconfigurations, some other appropriate algorithm or technique is used.

In addition to the automatic calibration operation, the process 600 atstep 608 may apply appropriate further processing to the signals toextract the physiological signal or signals. At step 610, the process600 provides a graphical display of one or more physiological parametersbased on the processed signal or signals. Until monitoring isdiscontinued, the process 600 of certain embodiments generally continuesto process the signal and display the physiological parameter byrepeating steps 608 and 610.

Further Compatible Embodiments

Multiple sensors are often applied to a medical patient to providephysiological information about the patient to a physiological monitor.Some sensors, including certain optical and acoustic sensors, interfacewith the monitor using a cable having power, signal, and ground lines orwires. One or more these lines can pose an electric shock hazard whenmultiple sensors are attached to the patient. If an electrical potentialexists in the ground line, for instance, a ground loop can form in thepatient or in the ground line, allowing unwanted current to pass throughthe patient through the ground line. Power fluctuations or surges, suchas from a defibrillator, can potentially harm the patient and damage themonitor or the sensors.

This disclosure describes decoupling circuitry that can be used toprevent or substantially prevent ground loops and other current loopsfrom forming. Using decoupling circuitry in this manner can be referredto as providing sensor isolation, patient isolation, patient protection,sensor decoupling, or the like. Currently-available physiologicalmonitors that connect to one sensor at a time using a single cable maynot have this decoupling circuitry. Upgrading these monitors to receivetwo or more sensors can create the shock hazard described above unlessprotective circuitry is added to these monitors. For existingsingle-sensor monitors, adding this circuitry might require a costlyupgrade of the monitors' internal components. For new single-sensormonitors, the decoupling circuitry could be added during manufacturing.But this approach would be cost-inefficient for buyers who wish to useonly one sensor with the device.

Accordingly, in certain embodiments, the decoupling circuitry isprovided in a medical cable assembly. The medical cable assemblyincludes, in some embodiments, a splitter cable that interfaces multiplephysiological sensors with a single sensor port on a physiologicalmonitor. Advantageously, in certain embodiments, the medical cableassembly allows multiple sensors to connect to a monitor while reducingthe risk of electric shock to a patient.

FIGS. 7A and 7B illustrate embodiments of physiological monitoringsystems 700A, 700B interfacing with multiple sensor assemblies 750. Thephysiological monitoring systems 700A, 700B each include a physiologicalmonitor 710, a splitter cable 720, two cables 730, and two sensorassemblies 750. The physiological monitoring systems 700A, 700B mayinclude all of the features of the physiological monitoring system 100described above.

In the physiological monitoring system 700A of FIG. 7A, a patientdecoupling circuit 740 a is provided in one of the cables 730 b. In thephysiological monitoring system 700B of FIG. 7B, the patient decouplingcircuit 740 b is provided in the splitter cable 720 b. These patientdecoupling circuits 740 a, 740 b can reduce or prevent ground loops fromforming in the patient and/or in the physiological monitoring system700. Although not shown, a decoupling circuit could instead be providedin one or both of the sensor assemblies 750.

The physiological monitor 710 processes and outputs physiologicalinformation received from sensors included in the sensor assemblies 750a, 750 b. The physiological monitor 710 of certain embodiments includesa power decoupling circuit 715, a processing board 717, and a connector719. The power decoupling circuit 715 may be a transformer or the likethat decouples power (e.g., AC electrical power) received from a powersource (such as an electrical outlet) and the circuitry of thephysiological monitor 710. The power decoupling circuit 715 prevents orsubstantially prevents current spikes from damaging the other componentsof the physiological monitor 710 or the patient. In embodiments wherethe physiological monitor 710 receives power from another source, suchas batteries, the power decoupling circuit 715 may not be included.

The processor 717 of certain embodiments is a microprocessor, digitalsignal processor, a combination of the same, or the like. The processor717 receives power from the power decoupling circuit 715. In someimplementations, the processor 717 processes physiological signalsreceived from the sensors 750 and outputs the processed signals to adisplay, storage device, or the like. In addition, the processor 717 maycommunicate with an information element (e.g., a memory device) includedin a cable or sensor. Information elements are discussed in greaterdetail herein with respect to FIGS. 3 through 6 and 11 through 17.

The connector 719 includes a physical interface for connecting a cableassembly to the physiological monitor 710. In the embodiment shown inFIGS. 7A and 7B, a single connector 719 is provided. Additionalconnectors 719 may also be included in some implementations. Oneembodiment of a physiological monitor having additional connectors 719is described below with respect to FIG. 8.

The splitter cable 720 is provided in some embodiments to enable thephysiological monitor 710 having one connector 719 to interface withmultiple sensors 750. The splitter cable 720 interfaces with theconnector 719 through a monitor connector 721 in the splitter cable 720.In the depicted embodiment, where the splitter cable 720 interfaces withtwo sensors 750, cable sections 722 of the splitter cable 720, whichbranches into two sections generally forming a “Y” shape or the like.Thus, the splitter cable 720 can be a Y cable or the like. While thesplitter cable 720 is shown forming a “Y” shape, other configurationsand shapes of the splitter cable 720 may be used. For example, thesplitter cable 720 could branch into more than two cable sections 722 tointerface with more than two sensors 750.

The cable sections 722 are shown connected to the monitor connector 721and two cable connectors 723. In some embodiments, the cable sections722 branch into more than two parts and connect to more than two cableconnectors 723. In addition, in some embodiments the splitter cable 720couples directly to two or more sensors 750.

Some embodiments of the splitter cable 720 include one or more lines,conductors, or wires per cable connector 723. One line might beprovided, for example, to interface with one or more electrocardiograph(ECG) sensors. Two or three lines might be provided per cable connector723, for example, to interface with an optical or acoustic sensor. Forinstance, three lines might be provided, including a power line, asignal line, and a ground line (see FIGS. 4 and 5). The power linepowers the sensor 750, the signal line receives signals from the sensor750, and the ground line acts as an electrical return path for the powerand/or signal lines. In some embodiments, one or more of the linescoming from one sensor 750 a are placed at a predetermined distance fromone or more of the lines coming from another sensor 750 b to reducecross-talk interference between the sensors 750. One or moreelectromagnetic shielding and/or insulating layers may also be providedto help reduce cross-talk. Lines from different sensors may merge into ashared line that connects electrically to the monitor 710, and some formof multiplexing might be used to allow the different sensors tocommunicate along the shared lines.

The cables 730 a, 730 b interface with the splitter cable 720 in thedepicted embodiment through cable connectors 731. In certainembodiments, each cable 730 also includes a cable section 732 and asensor connector 733 that connects to a sensor 750. The cable section732 in some implementations includes one or more lines or wires forcommunicating with the sensor 750. For example, a power line, sensorline, and ground line may be provided that correspond to the power line,sensor line, and ground line in the example splitter cable 720 describedabove.

In an embodiment, one of the cables 730 includes the decoupling circuit740 a. In FIG. 7A, for example, the decoupling circuit 740 a is shown inthe cable section 732 of the cable 730 b. The decoupling circuit 740 amay also be placed in the cable connector 731 or the sensor connector733, or in a combination of one or more of the connectors 731, 733and/or the cable section 732. In another exemplary embodiment, FIG. 7Bshows that the decoupling circuit 740 b can be included in one of thecable sections 722 of the splitter cable 720 b. The decoupling circuit740 b may also be placed in the monitor connector 721 or the sensorconnector 723, or in a combination of the cable sections 722 and/or oneor more of the connectors 721, 723.

Multiple decoupling circuits 740 may also be provided in one or more ofthe cables 730 and/or in the splitter cable 720 in other embodiments. Inparticular, in one embodiment when N cables 730 are provided (or onesplitter cable 720 with N connectors 723), N−1 decoupling circuits 740are provided in N−1 of the cables 730 or in the various sections of thesplitter cable 720.

The decoupling circuit 740 of certain embodiments electrically decouplesa sensor 750 from the physiological monitor 710. In addition, thedecoupling circuit 740 can electrically decouple one sensor (e.g., thesensor 750 b) from another sensor (e.g., the sensor 750 a) in certainembodiments. The decoupling circuit 740 can be a transformer, anoptocoupler, a DC-DC converter, a switched-mode converter, or the likeor a combination of the foregoing. In addition, the decoupling circuit740 can include one or more optical fibers. An optical fiber may be usedin place of the signal line, for example. More detailed embodiments ofthe decoupling circuit 740 are described below with respect to FIGS. 9and 10.

The sensors 750 connect to the sensor connectors 733 of the cables 730.In an embodiment, one of the sensors 750 is an optical sensor, such as amultiple wavelength oximetry sensor. The other sensor 750 in oneembodiment is an acoustic sensor. In addition, the sensor 750 may be anacoustic sensor that also monitors ECG signals, such as is described inU.S. Provisional Application No. 60/893,853, titled “Multi-parameterPhysiological Monitor,” and filed Mar. 8, 2007, the disclosure of whichis hereby incorporated by reference in its entirety and U.S. applicationSer. No. 12/044,883, titled “SYSTEMS AND METHODS FOR DETERMINING APHYSIOLOGICAL CONDITION USING AN ACOUSTIC MONITOR,” and filed Mar. 7,2008. Many other types of sensors 250 can also be used to monitor one ormore physiological parameters.

FIG. 8 illustrates another embodiment of a physiological monitoringsystem 800 having multiple cables 730. The physiological monitoringsystem 800 may have certain of the features of the physiologicalmonitoring systems 100, 700 described above. For example, like thephysiological monitoring system 700 described above, the physiologicalmonitoring system 800 includes a physiological monitor 810, two cables730, and two sensors 750. In the physiological monitoring system 800, adecoupling circuit 740 is provided in one of the cables 730 b.

Like the physiological monitor 710, the physiological monitor 810includes a power decoupling circuit 715 and a processor 717. Unlike thephysiological monitor 710, however, the physiological monitor 810includes two connectors 819 for interfacing directly with two cableswithout using a splitter cable. To save costs for users who will useonly one sensor 750 with the physiological monitor 810, a decouplingcircuit 740 is not provided in the physiological monitor 810. Instead,the decoupling circuit 740 can be provided in a separate cable 730 bthat can be used with the physiological monitor 810.

For example, a user might use one cable 730 a and sensor 750 a at a timewith the physiological monitor 810. Since only one sensor 750 a is beingused, ground or other current loops are less likely to form in thepatient. If the user later wishes to use additional sensors 750, theuser can obtain a cable 730 b having the decoupling circuit 740. Usingthe cable 730 b can beneficially allow the user to continue using thephysiological monitor 810 without performing an upgrade to thephysiological monitor's 810 internal components.

FIG. 9 illustrates another embodiment of a physiological monitoringsystem 900 having multiple cables 930. The physiological monitoringsystem 900 may have certain of the features of the physiologicalmonitoring systems 100, 700, 300 described above. For example, like thephysiological monitoring systems described above, the physiologicalmonitoring system 900 includes a physiological monitor 910, two cables930, and two sensors 950. The features described with respect to FIG. 9may also be applied to a monitoring system having a splitter cableinstead of multiple cables.

In the depicted embodiment, the cables 930 are shown connected to thephysiological monitor 910 and to the sensors 950. Connectors 919 in thephysiological monitor 910 couple with connectors 931 of the cables 930,and connectors 933 of the cables couple with connectors 951 of thesensors 950. A cable section 932 extends between the connectors 931, 933of each cable.

The cable 930 a includes a power line 962 a, a ground line 964 a, and asignal line 966 a extending from the connector 931 to the connector 933.These lines form electrical connections with corresponding power,ground, and signal lines in the connector 919 a of the physiologicalmonitor 910 and in the connector 951 a of the sensor 950 a. Likewise,the cable 930 b includes a power line 962 b, a ground line 964 b, and asignal line 966 b. These lines form electrical connections withcorresponding power, ground, and signal lines in the connector 919 b ofthe physiological monitor 910. In addition, these lines extend from theconnector 931 to a decoupling circuit 940. A power line 972, ground line974, and signal line 976 extend from the decoupling circuit 940 to theconnector 931 to form electrical connections with corresponding power,signal, and ground lines in the connector 951 b of the sensor 950 b. Thecable section 932 can also include one or more electrical insulation andshielding layers, materials, or fillers. Although not shown, one or moreof the cables 930 a, 930 b may also include one or more communicationslines for communicating with information elements.

In the depicted embodiment, the ground line 964 a is connected to theground line 964 b in the physiological monitor 910 through line 964 c.When both sensors 950 are placed on a patient, the ground lines 964 aand 979 b may also be in electrical communication through the patient,as illustrated by the dashed line 984. If the decoupling circuit 940were not present in one of the cables 930, a ground loop might be formedalong the lines 964 a, 964 b, 964 c, 974, and 984 (illustrated with boldlines) due to, for example, a difference in electrical potential in thelines 964 a, 964 b, 964 c, and 974. While not shown in bold, currentloops might also form in some cases among the power lines 962 a, 962 b,972 or the signal lines 966 a, 966 b, 976.

Advantageously, in certain embodiments, the decoupling circuit 940reduces the risk of a ground or other loop forming by decoupling one ormore of the power lines 962 b, 972, the signal lines 964 b, 974, or theground lines 964 b, 974. More detailed embodiments illustrating how thedecoupling circuit 940 could decouple one or more lines is describedbelow with respect to FIGS. 10A through 10C and FIG. 3C.

While only one decoupling circuit is shown, in other embodiments,multiple decoupling circuits may be provided in one cable 930. Forinstance, a first decoupling circuit could be connected to the powerline 962 b and the ground line 966 b, and a second decoupling circuitcould be connected to the signal line 964 b and to the ground line 966b. In addition, in certain embodiments, there may be a decouplingcircuit in each cable 930 a, 930 b.

FIG. 10A illustrates a more detailed embodiment of a decoupling circuit1040 a suitable for use with any of the embodiments discussed herein.The decoupling circuit 1040 a may include all the features of thedecoupling circuits 740, 840, and 940 described above. For example, thedecoupling circuit 1040 a may be included in a medical cable assembly,such as a splitter cable, medical cable, or the like, or in a sensorassembly. The decoupling circuit 1040 a can decouple electrical signalsand prevent or reduce ground or other conducting loops from forming andcan protect against current surges in a multi-sensor physiologicalmonitoring system.

The decoupling circuit 1040 a is shown within dashed lines. Thedecoupling circuit 1040 a of various embodiments receives a signal line1062 a, a power line 1066 a, and a ground line 1064 a. These lines canbe connected to a physiological monitor (not shown). In addition, thedecoupling circuit 1040 a receives a signal line 1072 a, a power line1076 a, and a ground line 1074 a, which may be connected to a sensor(not shown).

In an embodiment, the power line 1066 a provides power from aphysiological monitor to the decoupling circuit 1040 a, which providesthe power to the sensor through the power line 1076 a. The signal line1072 a provides a physiological signal from the sensor to the decouplingcircuit 1040 a, which provides the physiological signal to the monitorthrough the signal line 1062 a. The ground lines 1064 a and 1074 a actas return paths for their respective signal and power lines 1062 a, 1066a, 1072 a, 1076 a.

The decoupling circuit 1040 a, in some implementations, includes anoptocoupler 1042 a and a transformer 1044 a. The optocoupler 1042 areceives physiological signals from the sensor line 1072 a and providesthe signals to the sensor line 1062 a optically using, for example, aphotodiode 1046 a and a phototransistor 1048 a. Because the signals aretransmitted optically, in certain embodiments there is no electricalcontact between the signal lines 1062 a, 1072 a. Similarly, thetransformer 1044 a provides power from the power line 1066 a to thepower line 1076 a without electrical contact between the lines 1066 a,1076 a. Through mutual inductance, electromagnetic energy is transferredfrom one winding 1050 a of the transformer 1044 a to another winding1052 a. Because the signals are transmitted using mutual inductance,there is no electrical contact between the power lines 1066 a, 1076 a.

In certain embodiments, because the power lines 1066 a, 1076 a andsignal lines 1062 a, 1072 a are electrically decoupled, the ground lines1064 a, 1074 a can also be electrically decoupled. As shown, a groundline 1043 a of the optocoupler 1042 a on the monitor side connects tothe ground line 1064 a, and a ground line 1053 a of the optocoupler 1042a on the sensor side connects to the ground line 1074 a. As a result,the risk of ground loops forming in the patient may be reduced oreliminated.

Many other configurations of the decoupling circuit 1040 a may beemployed. For instance, a second optocoupler 1042 a may be used in placeof the transformer 1044 a, or a second transformer 1044 a may be used inplace of the optocoupler 1042 a. In addition, some forms of DC-DCconverters or switched mode converters may be used in place of eitherthe optocoupler 1042 a or the transformer 1044 a. Alternatively, one ormore optical fibers may be used.

Moreover, one or more optical fibers can be used instead of theoptocoupler 1042 a or the transformer 1044 a. Because the optical fiberstransmit optical, rather than electrical signals, using optical fibersin certain embodiments beneficially reduces the likelihood of groundloops forming in the patient. In one example embodiment, the optocoupler1042 a in FIG. 10A is replaced with an optical fiber, but thetransformer 1044 a is still included in the decoupling circuit 1040 a.The optical fiber allows signals to be transmitted through the signalline while preventing current from passing through the signal line. Inaddition, if optical fibers are used for the signal lines of multiplesensors, the optical fibers can also reduce cross-talk interferenceamong the signal lines.

FIG. 10B illustrates an embodiment of a circuit 1000B that includes adecoupling circuit 1040 b. The decoupling circuit 1040 b may include allthe features of the decoupling circuits 240, 340, and 440 describedabove. For example, the decoupling circuit 1040 b may be included in amedical cable assembly, such as a splitter cable, medical cable, or thelike, or in a sensor assembly.

The decoupling circuit 1040 b is shown decoupling a signal line 1062 bconnected to a monitor from a signal line 1072 b connected to a sensor.In the depicted embodiment, the decoupling circuit 1040 b is an analogoptocoupler. The decoupling circuit 1040 b includes a transmittingphotodiode 1041 and two receiving photodiodes 1045 a, 1045 b forfeedback control.

The transmitting photodiode 1041 receives physiological signals from thesignal line 1072 b via a feedback circuit 1057 (described below). Thetransmitting photodiode 1041 transmits the physiological signals to bothof the receiving photodiodes 1045 a, 1045 b. The receiving photodiode1045 b transmits the signals it receives from the transmittingphotodiode 1041 to the monitor via signal line 1062 b. The receivingphotodiode 1045 a transmits the signals it receives to a feedbackcircuit 1057.

Many diodes are inherently unstable due to nonlinearity and driftcharacteristics of the diodes. As a result of such instability, thesignal produced by the transmitting photodiode 1041 may not correspondto the signal provided by the signal line 1072 b from the sensor. Thereceiving diode 1045 a can therefore be used as a feedback diode toprovide a received signal to the feedback circuit 1057.

The feedback circuit 1057 can include an amplifier or the like thatadjusts its output provided to the transmitting photodiode 1041 based atleast partly on a difference between the signal of the transmittingphotodiode 1041 and the receiving diode 1045 a. Thus, the feedbackcircuit 1057 can correct for errors in the transmitted signal viafeedback from the feedback or receiving diode 1045 a.

FIG. 10C illustrates another embodiment of a circuit 1000C that includesa decoupling circuit 1040 c. The decoupling circuit 1040 c may includeall the features of the decoupling circuits 740, 840, and 940 describedabove. For example, the decoupling circuit 1040 c may be included in amedical cable assembly, such as a splitter cable, medical cable, or thelike, or in a sensor assembly.

The decoupling circuit 1040 c is shown decoupling a power line 1066 cconnected to a monitor from a power line 1076 c connected to a sensor.The decoupling circuit 1040 c can be used together with the decouplingcircuit 1040 b of FIG. 10B in some embodiments. For example, thedecoupling circuits 1040 b, 1040 c may be provided on the same circuitboard. Like the decoupling circuit 1040 b, the decoupling circuit 1040 cuses feedback to dynamically correct or control the output of thedecoupling circuit 1040 c.

The decoupling circuit 1040 c in the depicted embodiment is a flybacktransformer having two primary windings 1050 c, 1051 c and one secondarywinding 1052 c. The primary winding 1050 c receives power (VIN) from thepower line 1066 c. A switched mode power supply 1060 also receives power(VIN) from the power line 1066 c. In an embodiment, the switched modepower supply 1060 is a DC-DC converter or the like. A switch pin 1062 ofthe power supply 1060 can be enabled or otherwise actuated to allowpower (VIN) to cycle through the primary winding 1050 c. The switch pin1062 may cause the power to be switched according to a predeterminedduty cycle. Feedback may be used, as described below, to maintain astable or relatively stable duty cycle.

As the primary winding 1050 c is being energized, the primary winding1050 c may store energy in itself and in a core 1063 of the transformer.Through inductive coupling, this energy may be released into thesecondary winding 1052 c and into the primary winding 1051 c. Thepolarity of the windings 1052 c, 1051 c (as indicated by the dots on thewindings) may be the same to facilitate the transfer of energy.Likewise, the polarity of the windings 1052 c, 1051 c may differ fromthe polarity of the winding 1050 c.

Like the feedback receiving photodiode 1045 a described above, theprimary winding 1051 c acts as a flyback winding in certain embodimentsto transmit the received power as a feedback signal. A rectifier 1065rectifies the power received from the primary winding 1051 c andprovides a feedback power VFB to a feedback pin 1066 of the power supply1060. The power supply 1060 may then use the difference between thereceived feedback power VFB and the transmitted power VIN to adjust VINto compensate for any error in the transmitted power. For example, thepower supply 1060 can adjust the duty cycle described above based atleast partly on the error, e.g., by increasing the duty cycle if the VFBis low and vice versa. This flyback operation can advantageouslymaintain a stable or substantially stable power duty cycle despitevarying load conditions on the decoupling circuit 1040 c.

The secondary winding 1050 c can provide an output to a linear powersupply 1070, which may rectify the received power, among otherfunctions. The linear power supply 1070 may provide the power to thepower line 1076 c for transmission to the sensor.

FIGS. 11A and 11B illustrate an example splitter cable 1120. FIG. 11Adepicts a side view of the splitter cable 1120 while FIG. 11B depicts abottom view of the splitter cable 1120. The splitter cable 1120 includesa housing 1107 that includes a circuit board 1140 having a decouplingcircuit, show in phantom. The housing 1107 further includes wires 1142,also shown in phantom, in communication with the circuit board 1140 andwith first cable sections 1130 a, 1130 b and a second cable section 1122of the splitter cable 1120. The housing 1107 is also shown connected tothe second cable section 1122, which in turn connects to a connector1121. In an embodiment, the connector 1121 is used to connect thesplitter cable 1120 to a physiological monitor.

The housing 1107 of the splitter cable 1120 further connects to one ofthe first cable sections 1130 a through a connector 1131. Another one ofthe first cable sections 1130 b is integrally coupled to the housing1107 of the splitter cable 1120 in the depicted embodiment. In oneimplementation, the splitter cable 1120 and the cable 1130 b are used toobtain physiological information from a single sensor, and the cable1130 a may be added to the splitter cable 1120 to obtain physiologicalinformation from an additional sensor. It should be noted that in analternative embodiment, the first cable section 1130 b is not integrallyattached to the housing 1107 but instead attaches to the housing using asecond connector. Or, both of the first cable sections 1130 could beintegral to the housing 1107.

The circuit board 1140 interfaces with both first cable sections 1130 a,1130 b and with the second cable section 1122. The circuit board 1140may include, for example, one or more integrated circuits or discretecircuit components that together are implemented as a decouplingcircuit. In addition, the circuit board 1140 can include one or moreinformation elements for storing various forms of data.

Turning to FIG. 12, additional embodiments of cable assemblies 1230 willbe described. As explained above with respect to FIG. 1, cableassemblies having two separate cables may be provided in someembodiments. These separate cables can include a sensor cable 1212 andan instrument cable 1214. In one embodiment, the sensor cable 1212 is ashort, lightweight cable, adapted to facilitate comfortable attachmentof sensors to a medical patient. In certain embodiments, the instrumentcable 1214 is a heavier, sturdier cable, acting as a durable interfacebetween the sensor cable 1212 and a monitor. Sensor cables 1212 andinstrument cables 1214 may be periodically replaced. Periodicreplacement is advantageous in certain embodiments for a wide variety ofreasons. For example, the cable can become soiled or damaged, causingcable failure, inaccurate results, or patient cross-contamination.

In addition, one or more decoupling circuits or information elements(see FIGS. 3 and 15) may be incorporated into the cable assembly 1230 incertain embodiments. The information elements may store cable managementinformation related to usage of the cable assembly and devices connectedto the cable assembly. The information elements may also store patientcontext information related to patient identification and patientmovement (flow) among hospital departments, thereby tracking thepatient's progress throughout the hospital. Examples of patient contextinformation are described more fully in U.S. patent application Ser. No.11/633,656, titled “Physiological Alarm Notification System,” filed Dec.4, 2006, which is hereby incorporated by reference in its entirety.Moreover, the information elements can store physiological informationin some implementations. The information elements may further storecalibration information related to the particular components presentlyattached to the system. For example, each information element may storeinformation related to behavioral characteristics of the stage to whichit is attached (e.g., a sensor, cable, etc.). The monitoring device mayuse such information to automatically calibrate a multi-stage sensorpath, for example. Example calibration information is described herein,with respect to FIGS. 2 through 6, for example.

Referring again to FIG. 12, a sensor cable 1212 is shown connected to asensor assembly 1250. The sensor cable 1212 may include a flexible cablesection 1232 having an elongated shape, a connector 1251 for interfacingwith a sensor assembly 1250, and a connector 1237 for interfacing withan instrument cable 1214. The flexible nature of the cable section 1232in one embodiment is provided to enable greater patient comfort, as thepatient can move more easily with a flexible sensor cable 1212 attached.

The depicted example instrument cable 1214 includes a stiff orrelatively rigid, durable cable section 1234 having an elongated shape,a connector 1235 for interfacing with the sensor cable 1212, and aconnector 1231 for interfacing with a physiological monitor. As theinstrument cable 1214 of various embodiments is not connected directlyto the patient, the instrument cable section 1234 may be less flexible(and more durable) than the sensor cable section 1232, thereby extendingthe life of the instrument cable 1214.

Decoupling circuitry and/or information elements may be included withinthe sensor cable 1212, the instrument cable 1214, or both. Thedecoupling circuits and/or information elements may be placed in any ofthe connectors 1237, 1251, 1235, or 1231 or in either cable section1232, 1234. In other embodiments, one or more information elements maybe included in any of the splitter cables described above. Inalternative embodiments, the sensor cable 1212 can be a splitter cable.

FIG. 13 illustrates an embodiment of a physiological monitoring system1300 which may be used in a hospital, nursing home, or other locationwhere medical services are administered (collectively “hospital”).Certain aspects of the physiological monitoring system 1300 aredescribed in more detail in U.S. patent application Ser. No. 11/633,656,titled “Physiological Alarm Notification System,” filed Dec. 4, 2006,which is hereby incorporated by reference in its entirety.

The physiological monitoring system 1300 of certain embodiments includespatient monitoring devices 1302. The patient monitoring devices 1302 ofvarious embodiments include sensors 1350, one or more physiologicalmonitors 1310, cables 1330 attaching the sensors 1350 to the monitors1310, and a network interface module 1306 connected to one or morephysiological monitors 1310. Each patient monitoring device 1302 in someembodiments is part of a network 1320 of patient monitoring devices1302. As such, the patient monitoring devices 1302 in these embodimentscan communicate physiological information and alarms over a hospitalwireless network (WLAN) 1326 or the Internet 1350 to clinicians carryingend user devices 1328, 1352.

The network interface module 1302 of certain embodiments transmitsphysiological information on demand or in the event of an alarm to theend-user devices 1328, 1352 and/or transmits the alarm to a centralnurses' station. Alternatively, the network interface module 1302transmits information and alarms to a server 1336. The server 1336 is acomputing device, such as an appliance server housed in a data closet ora workstation located at a central nurses' station. The server 1336passes the information or alarms to the end user devices 1328, 1352 orto the central nurse's station. The alarms may be triggered when certainphysiological parameters exceed safe thresholds, thereby enablingclinicians to respond rapidly to possible life-threatening situations.Situations giving rise to an alarm might include, for example, decreasedheart rate, respiratory rate, low SpO₂ levels, or any otherphysiological parameter in an abnormal range.

The network interface module 1302 in one embodiment also performs cablemanagement by generating an alarm when one of the cables 1330 is nearingthe end of its life. The network interface module 1302 determineswhether the cable's 1330 life is close to expiring by, for example,analyzing some or all of the data described above with respect to FIG.4. In one embodiment, if the network interface module 1302 determinesthat the cable life is close to expiration, the network interface module1302 provides an expiration message as an alarm.

In one embodiment, the server 1336 receives this expiration message. Theserver 1336 then checks an inventory stored in a database 1338 to see ifa replacement cable is available. If there is no replacement cable inthe inventory, the server may forward the message to a supplier 1370over the Internet 1350 (or through a WAN, leased line or the like). Inan embodiment, the server 1336 transmits an email message to a supplier1370 that indicates the cable location, cable condition, and/or othercable usage data. The supplier 1370 in one embodiment is a cable seller.Upon receiving the message, the supplier 1370 may automatically ship anew cable to the hospital. Consequently, cable 1330 inventories are ableto be maintained with minimal or no user intervention in thisimplementation, and cables 1330 may be replaced preemptively, beforecable failure.

In additional embodiments, the network interface module 1306 may monitorsensor utilization, such as the number of sensors used during thepatient's stay, the types of sensors, and the length of time in usebefore replacement. Such data can be used by the hospital topreemptively plan restocking and set department par inventory levels. Inaddition, a supplier can use this data to restock the hospital orimplement a just in time inventory control program. Moreover, suchinformation can be used by the supplier to improve overall cablereliability and for the hospital to better plan and manage consumables.

The network interface module 1306 of various implementations alsoperforms context management. In one embodiment, context managementincludes associating context information with physiological informationto form a contextual data package. As described above, contextinformation may include patient identification data and patient flowdata. In addition, context information may include context informationrelated to usage of the network interface module 1306 and contextinformation related to the network. For example, this additional contextinformation may include an identification number of the networkinterface module 1306, time stamps for events occurring in thephysiological monitoring system 1300, environmental conditions such aschanges to the state of the network and usage statistics of the networkinterface module 1306, and identification information corresponding tothe network (e.g., whether the network connection is WiFi or Ethernet).

The network interface module 1306 receives context information in oneembodiment by a nurse entering the information in the network interfacemodule 1306 or from the server 1336. The network interface module 1306transmits or communicates the contextual data package to cliniciansduring an alarm, upon clinician request, or on a scheduled basis. Inaddition, the network interface module 1306 may transmit a continuousstream of context information to clinicians.

The server 1336 receives contextual data packages from a plurality ofnetwork interface modules 1306 and stores the contextual data package ina storage device 1338. In certain embodiments, this storage device 1338therefore archives long-term patient data. This patient data may bemaintained even after the patient is discharged. Thus, contextinformation may be stored for later analysis to, for example, developpatient care metrics and improve hospital operations. The patient datacould be deleted after the care metrics are developed to protect patientprivacy.

Although the functions of cable management and context management havebeen described as being performed by the network interface module 1306,in certain embodiments, some or all of these functions are insteadperformed by the physiological monitor 1310. In addition, thephysiological monitor 1310 and the network interface module 1306 mayboth perform cable management and/or context management functions.

FIG. 14 illustrates an embodiment of a usage tracking method 1400 fortracking the life of a medical cable. In one implementation, the usagetracking method 1400 is performed by the network interface module and/orone of the physiological monitors described above. More generally, theusage tracking method 1400 may be implemented by a machine having one ormore processors. Advantageously, in certain embodiments, the usagetracking method 1400 facilitates replacing a cable prior to failure ofthat cable.

The usage tracking method 1400 begins by obtaining sensor parametersfrom a sensor at block 1402. At block 1404, cable usage informationstored in an information element is tracked. The cable usage informationcan be tracked by at the same time or substantially the same time asobtaining sensor parameters from the sensor. Alternatively, the cableusage information may be tracked by determining cable usage at the startor end of monitoring (e.g., obtaining sensor parameters), orperiodically throughout monitoring. In addition, the cable usageinformation may be tracked even if the block 1402 were not performed,e.g., when the monitor is not currently obtaining parameters from thesensor.

At decision block 1406, it is determined whether the cable's life isclose to expiring (or whether the cable has in fact expired). Thisdetermination may be made using the data described above with respect toFIG. 4. In addition, the this determination may be made using sensorlife functions applied analogously to the life of the cable.

If it is determined that the cable life is close to expiration (or hasexpired), an expiration message is provided at block 1408. In oneembodiment, this message is provided as an alarm on the monitor or at acentral nurses' station. The message may also be provided to aclinician's end user device, which may be located in the hospital or ata remote location. Moreover, the message may be provided to a server,which forwards the message to a supplier, which ships a new cable. In anembodiment, the message is an email that indicates the cable location,cable condition, and/or other cable usage data. If, however, it isdetermined that the cable life is not close to expiration (or is notexpired), the usage tracking method 1400 loops back to block 1402 tocontinue monitoring. In effect, the usage tracking method 1400 maycontinue monitoring and/or tracking cable usage information until thecable is close to expiration or has expired.

FIG. 15 illustrates an embodiment of a cable inventory method 1500 forcontrolling cable inventory. The cable inventory method 1500 may beperformed by a server, such as the server 1038 described above. Moregenerally, the cable inventory method 1500 may be implemented by amachine having one or more processors. In one embodiment, the method1500 is performed in response to the method 1400 providing an expirationmessage at step 1408.

At block 1502, an expiration message is received from a monitor,indicating that a cable is close to expiration or has expired. At block1504, an inventory is checked for a replacement cable. This inventorymay be a hospital inventory, a record of which may be maintained in ahospital database or the like.

If it is determined at decision block 1506 that there is no replacementcable in the inventory, a new cable is ordered automatically to order aat block 1508. In an embodiment, this block 1508 is performed byelectronically contacting a supplier to order the cable, for example, bysending a request over a network such as the Internet. Consequently, incertain embodiments, the cable inventory method 1500 enables the cableto be replaced preemptively, before cable failure. If, however, there isa replacement cable in inventory, the cable inventory method 1500 ends.However, in alternative embodiments, the cable inventory method 1500orders a replacement cable regardless of the inventory, such that apredetermined level of cable inventory is maintained.

In additional embodiments, the cable inventory method 1500 may monitorsensor utilization, such as the number of sensors used during thepatient's stay, the types of sensors, and the length of time in usebefore replacement. Such data can be used by the hospital topreemptively plan restocking and set department par inventory levels. Inaddition, a supplier can use this data to restock the hospital orimplement a just-in-time program. Moreover, such information can be usedby the supplier to improve overall cable reliability, and for thehospital to better plan and manage consumables.

FIG. 16 illustrates an example context management method 1600 formanaging patient context. In an embodiment, the context managementmethod 1600 is performed by a physiological monitor, such as any of themonitors described above. More generally, certain blocks of the contextmanagement method 1600 may be implemented by a machine having one ormore processors. The context management method 1600, in certainembodiments, advantageously enables a patient to be assigned a cablewith a unique identifier upon the first connection of the cable to thepatient or to a monitor.

At block 1600, a cable is connected to a monitor, for example, by aclinician such as a nurse. Thereafter, a temporary patient ID isassigned to the cable at block 1604. The temporary ID may beautomatically assigned when power is provided to the information elementin the cable, or a prompt may be provided to a clinician, who thenassigns the ID. In addition, the temporary ID may also be previousstored on the cable. The temporary patient ID enables the cable to beidentified as uniquely relating to the patient, prior to the patient'sidentification information being provided to the cable. The temporarypatient ID may be stored in the information element of the cable.

At block 1606, patient flow data is stored in the information element.The patient flow data may include flow data described above with respectto FIG. 4. For example, the patient flow data may include informationregarding connected devices, a department ID associated with the cable,and time spent by the cable in a department. By storing patient flowdata, the context management method 1600 can enable the flow of thepatient may be monitored upon connection of the cable to a monitor.Thus, even if the nurse neglects to identify the cable with the patient,the cable can have data indicating when it is being used on the same ora different patient.

At decision block 1608 it is determined whether a real patient ID hasbeen provided. If so, then the temporary ID is replaced with the realpatient ID at block 1610. The real patient ID may include any of thepatient identification information described above, with respect to FIG.4. If, however, it is determined that a real patient ID has not beenprovided, the context management method 1600 loops back to block 1606 tocontinue storing patient flow data in the information element.

FIG. 17 illustrates another example context management method 1700 formanaging patient context. In an embodiment, the context managementmethod 1700 is performed by one or more monitors, such as any of themonitors described above. More generally, certain blocks of the contextmanagement method 1700 may be implemented by a machine having one ormore processors.

At block 1702, a cable is connected to a monitor. In one embodiment,this block is performed by a clinician, such as a nurse. Patient flowdata is then stored in an information element at block 1704. The patientflow data may include the flow data described above with respect to FIG.4.

At decision block 1706, it is determined whether the cable has beenconnected to a new monitor. If it has, patient flow data is transferredfrom the cable to the new monitor at block 1708. In an embodiment, thenew monitor determines whether the cable has been connected to the newmonitor. Alternatively, the cable makes this determination. Transferringthe patient flow data to the new monitor provides, in certainembodiments, the advantage of enabling the monitor to know where thepatient has been in the hospital and for how long. If a new monitor hasnot been connected, the context management method 1700 ends.

FIG. 18 illustrates a front elevation view of an embodiment of acoextruded cable 1800. The coextruded cable 1800 can be used as a cableor cable section in place of any of the cables mentioned herein. Thecoextruded cable 1800 can advantageously reduce noise due to atriboelectric effect.

Noise can adversely affect acoustic signals detected by any of theacoustic sensors described herein by corrupting a waveform detected byan acoustic or other sensor. Once source of noise is triboelectricnoise, which can be present when a cable is squeezed, bringingconductors in the cable closer together. The closer the conductors are,the greater a capacitance can form between the conductors and/or betweenthe conductors and shielding. This capacitance can be a source oftriboelectric noise.

The example coextruded cable 1800 shown includes features that canreduce the amount of triboelectric noise generated by squeezing,rubbing, or other touching of the cable 1800. The cable 1800 includes anouter jacket 1810, which encompasses an outer shielding layer 1812. Theouter shielding layer 1812 can reduce ambient noise from reachingconductors 1820 that extend through the cable 1800. Insulation 1822surrounds each conductor 1820.

For ease of illustration, the coextruded cable 1800 is shown having twoconductors 1820. However, the features of the coextruded cable 1800 canbe extended to more than two conductors in certain embodiments. Forexample, more than two conductors can be surrounded by the insulation1822, or each of two or more conductors can be individually surroundedby insulation. Further, a group of acoustic sensor-related conductorscan be surrounded by insulation, and a group of optical sensor-relatedconductors can be surrounded by separate insulation.

Although not shown, the insulation 1822 can be shielded as well. Thus,in one embodiment, some or all acoustic sensor-related conductors can beshielded by a separate, inner shielding layer from the outer shieldinglayer 1812. Similarly, some or all optical sensor-related conductors canbe shielding by a separate, inner shielding layer from the outershielding layer 1812. One or both of the acoustic and opticalsensor-related sets of conductors can include their own inner layer ofshielding to reduce crosstalk between the acoustic and opticalsensor-related conductors. Reducing crosstalk can be particularlybeneficial for reducing noise on a communications line or lines in thecable 1800 (such as the serial transmission line 340 of FIGS. 3A, 3B).

Filling or substantially filling the space between the insulation 1822and the shielding layer 1812 is a coextruded material 1830. Thecoextruded material 1830 can be conductive PVC or the like that reducesspace between the conductors 1820, so that the cable 1800 does notcompress the conductors 1822 together as easily. The cable 1800 canstill be flexible or relatively flexible, however. Because the cable1800 may compress less than other cables, less triboelectric noise maybe generated. In addition, the conductive property of the conductivematerial 1830 can dissipate charge that builds up from the triboelectriccapacitance occurring between the conductors 1820 and/or between theconductors 1820 and the shielding 1812. This dissipative property of thematerial 1830 can further reduce noise.

Moreover, in certain embodiments, the outer jacket 1810 of the cable1800 can be coated or can be composed of a glossy material that has areduced coefficient of friction. Accordingly, materials that rub, brushagainst, or otherwise contact the outer jacket 1810 can slide smoothlyoff, thereby further reducing triboelectric noise.

Many other configurations of the cable 1800 are possible. For example,in one embodiment, the cable 1600 can include a flexible or “flex”circuit having conductive traces disposed on a substrate. Acousticand/or optical sensor-related conductors can be disposed in the flexcircuit (or in separate flex circuits). Further, the decouplingcircuitry described above can also be included in the flex circuit orcircuits. The flex circuit can be used as a sensor cable (see above), aninstrument cable (see above), as a hub cable (see below), portions ofthe same, or any combination of the same. Some examples of flex circuitsthat can be employed with any of the sensors, circuits, and cablesdescribed herein are described in U.S. Pat. No. 6,986,764, filed May 2,2002, titled “Flex Circuit Shielded Optical Sensor,” and U.S. Pat. No.7,377,794, filed Mar. 1, 2006, titled “Multiple Wavelength SensorInterconnect,” the disclosures of which are both hereby incorporated byreference in their entirety.

FIG. 19 illustrates example internal components of an example hub 1920or splitter cable. The hub 1920 shown is an example implementation ofthe hub 220 of FIG. 2 and can be used in place of any of the splittercables described herein. Advantageously, in certain embodiments, the hub1920 includes localized shielding 1942 to reduce the effects ofelectromagnetic noise on one or more physiological signals.

The hub 1920 includes connectors 1910, 1912 that connect to sensor orpatient cables (see, e.g., FIG. 2). For purposes of illustration, theconnector 1910 can be connected to an optical sensor via a cable, andthe connector 1912 can be connected to an acoustic sensor via a cable.Other physiological sensors can be connected via cables to theconnectors 1910, 1912.

The connectors 1910, 1912 can be soldered to a printed circuit board(PCB) 1930 housed within the hub 1920. The PCB 1930 includes front-endsignal conditioning circuitry 1940, 1950, which can filter and conditionoptical signals and acoustic signals, respectively. The optical signalconditioning circuitry 1940 is disposed on a first area 1931 of the PCB1930, and the acoustic signal conditioning circuitry 1950 is disposed ona second area 1932 of the PCB 1930. An electrical decoupling region1933, which may be a nonconductive portion of the PCB 1930, separatesthe two areas 1931, 1932 of the PCB 1930 electrically. In otherembodiments, the two areas 1931, 1932 are separate PCBs. For example,one of the areas 1931, 1932 can be a daughter board attachable to theother area.

Decoupling circuitry 1956 electrically decouples the two areas 1931,1932. The decoupling circuitry 1956 can include any of the decouplingfeatures described above. For example, the decoupling circuitry 1956 caninclude a transformer 1954 for decoupling power signals and anoptocoupler 1952 for decoupling physiological signals. The decouplingcircuitry 1956 is shown coupled to the acoustic signal conditioningcircuitry 1950 in the depicted embodiment. In other embodiments, thedecoupling circuitry 1956 is coupled with the optical signalconditioning circuitry 1940. Decoupling circuitry can also be appliedseparately to both the optical and acoustic signal conditioningcircuitry 1940, 1950.

Due to regulations on winding insulation, to increase power efficiencyof the transformer 1954, and possibly other factors, the transformer1954 can be physically large relative to the size of other components inthe hub 1920. As a result, the hub 1920 can be relatively large. Thesize of the hub 1920 can be reduced in certain embodiments byincorporating the decoupling circuitry in a patient monitor (not shown)attached to the hub 1920. However, if the hub 1920 is used with existingmonitors that do not have decoupling circuitry, there may be little orno available space inside the monitor to fit a power-efficienttransformer 1954. Thus, including the transformer 1954 in the hub 1920can be advantageous to avoid making expensive modifications to anexisting patient monitor.

A schematic view of a cable 1922 is also shown. The cable 1922 isattached to the hub 1920. The cable 1922 can be permanently attached tothe hub 1920 or can be selectively detachable from the hub 1920. Thecable 1922 includes various example conductors 1961, 1965, 1967, and1969 in the depicted embodiment. Certain of the conductors 1961, 1965,1967, and 1969 can be used for power transmission, signal acquisition,and grounding, among other potential uses.

One of the conductors 1969 is shown as a first ground (G1) and iselectrically coupled with the optical signal conditioning circuitry1940. Another of the conductors 1961 is shown as a second ground (G2)and is electrically coupled with the decoupling circuit 1952 (and,optionally, the decoupling circuit 1954 as well). The first and secondgrounds 1969, 1961 are therefore separated for optical and acousticsignals, respectively, in the depicted embodiment. Providing separateground lines for the optical and acoustic signals can beneficiallyreduce crosstalk between these signals. The ground lines 1969, 1961 canbe connected together at the end of the cable 1922 (e.g., in a monitorconnector) or in a patient monitor (e.g., on a processing board).

To reduce noise, various components of the hub 1920 (e.g., including thePCB 1930) can be enclosed in an electromagnetic shield. Theelectromagnetic shield can be tied to ground conductors in the hub 1920,including the conductors 1961, 1969, and ground conductors in theacoustic signal conditioning circuitry 1950. However, doing so can causethe ground lines 1961, 1969 to come in electrical communication withboth electrically-decoupled areas 1931, 1932 of the PCB 1930. As aresult, patient isolation or decoupling would be broken, causingpotentially unsafe conditions.

Advantageously, in certain embodiments, shielding can be providedlocally within the hub 1920 instead of over all or substantially all ofthe components in the hub 1920. For instance, a local shield can encloseor at least partially enclose the acoustic circuitry 1950 and/orconnector 1912. Alternatively, a local shield can enclose or at leastpartially enclose the optical circuitry 1940 and/or connector 1910.Advantageously, in certain embodiments, substantial noise-reductionbenefit can be achieved by locally shielding one of the optical andacoustic circuitry 1940, 1950 with a local shield 1942. The local shield1942 can beneficially shield solder joints of the connector 1910 and/orcomponents 1940 as well. The shield can include a metal box, grate,perforated box, conductive glass, combinations of the same, or the like.

In other embodiments, a first local shield is disposed about the opticalcircuitry 1940 and a second local shield is disposed about the acousticcircuitry 1950. Each of these shields can be tied to different groundsor common potentials by virtue of the decoupling circuitry 1952, 1954.

Although the hub 1920 is illustrated with respect to optic and acousticsignals, more generally, the hub 1920 can interface with any type ofphysiological signals. Further, some or all of the features of the hub1920 can be used in certain applications outside of the medical fieldwhere cables are joined together in a single hub. Moreover, the featuresof the hub 1920 can be extended to more than two sensor cables. Such ahub can optionally include decoupling circuitry for some or all of thesensor cables that interface with the hub.

In some embodiments, one or more of the steps are performedsubstantially in parallel, in an overlapping manner, or in anotherorder. For example, some of the calibration information may changeduring operation (e.g., due to changes in operating temperatures and thelike). In such situations, the process 1900 can periodically orcontinually perform steps 1904 and 1906 to obtain, and automaticallyadjust to, the most up to date calibration information, providingimproved calibration and measurement accuracy. The process 1900 mayfurther continually or periodically perform step 1902 (e.g., duringprocessing), thereby detecting sensor path disconnection or changesduring use.

Those of skill in the art will understand that information and signalscan be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that can be referenced throughout theabove description can be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orstates. Thus, such conditional language is not generally intended toimply that features, elements and/or states are in any way required forone or more embodiments or that one or more embodiments necessarilyinclude logic for deciding, with or without author input or prompting,whether these features, elements and/or states are included or are to beperformed in any particular embodiment.

Depending on the embodiment, certain acts, events, or functions of anyof the methods described herein can be performed in a differentsequence, can be added, merged, or left out all together (e.g., not alldescribed acts or events are necessary for the practice of the method).Moreover, in certain embodiments, acts or events can be performedconcurrently, e.g., through multi-threaded processing, interruptprocessing, or multiple processors or processor cores, rather thansequentially.

Those of skill will further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Toclearly illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. Skilled artisans can implement the describedfunctionality in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of this disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein can be implementedor performed with a machine, such as a general purpose processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general purpose processor can be amicroprocessor, processor, controller, microcontroller, state machine,etc. A processor can also be implemented as a combination of computingdevices, e.g., a combination of a DSP and a microprocessor, a pluralityof microprocessors, one or more microprocessors in conjunction with aDSP core, or any other such configuration. In addition, the term“processing” is a broad term meant to encompass several meaningsincluding, for example, implementing program code, executinginstructions, manipulating signals, filtering, performing arithmeticoperations, and the like.

The steps of a method or algorithm described in connection with theembodiments disclosed herein can be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module can reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, a DVD, or any other form of storage medium known in the art. Acomputer-readable storage medium is coupled to the processor such thatthe processor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium can reside in anASIC. The ASIC can reside in a user terminal. In the alternative, theprocessor and the storage medium can reside as discrete components in auser terminal.

The modules can include, but are not limited to, any of the following:software or hardware components such as software object-orientedsoftware components, class components and task components, processes,methods, functions, attributes, procedures, subroutines, segments ofprogram code, drivers, firmware, microcode, circuitry, data, databases,data structures, tables, arrays, and/or variables.

In addition, although certain inventions have been disclosed in thecontext of certain embodiments, it will be understood by those skilledin the art that the inventions disclosed herein extend beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the inventions and obvious modifications and equivalentsthereof. In particular, while the system and methods have been describedin the context of certain embodiments, the skilled artisan willappreciate, in view of the present disclosure, that certain advantages,features and aspects of the acoustic signal processing system, device,and method may be realized in a variety of other applications andsoftware systems. Additionally, it is contemplated that various aspectsand features of the inventions disclosed herein can be practicedseparately, combined together, or substituted for one another, and thata variety of combination and subcombinations of the features and aspectscan be made and still fall within the scope of the inventions disclosedherein. Furthermore, the systems described above need not include all ofthe modules and functions described in certain embodiments. Thus, it isintended that the scope of the inventions disclosed herein disclosedshould not be limited by the particular disclosed embodiments describedabove, but should be determined only by the claims that follow.

What is claimed is:
 1. An acoustic physiological monitor configured todetermine an acoustic physiological parameter of a patient, the acousticphysiological monitor comprising: a sensor port configured to receiveone or more signals from a multi-stage sensor assembly including atleast a signal indicative of physiological sounds associated with apatient and a signal including calibration information, wherein: themulti-stage sensor assembly includes at least a first stage and a secondstage, the first stage and the second stage are removably connected toone another, and to the sensor port, in a serial manner, at least one ofthe first stage or the second stage comprises a splitter cable stage,the splitter cable stage comprises: a monitor connector operative toconnect to the sensor port, a plurality of sensor connectors eachoperative to connect to one of a plurality of physiological sensors, andone or more decoupling circuits operative to electrically decouple, fromeach other, sensors connected to the plurality of sensor connectors, themulti-stage sensor assembly includes electronic memories provided ineach of at least the first stage and the second stage, the electronicmemories store the calibration information, and the calibrationinformation includes at least a first characteristic associated with thefirst stage and a second characteristic associated with the secondstage; and one or more hardware processors configured to: receive asignal including at least the calibration information; adjust one ormore parameters of a signal processing algorithm of the one or morehardware processors, based on the calibration information including boththe first characteristic and the second characteristic, to compensatefor variations in components of the first stage and the second stage ofthe multi-stage sensor assembly; based on the adjusted one or moreparameters, generate a modified version of the signal indicative ofphysiological sounds associated with the patient; and determine anacoustic physiological parameter of the patient based upon the modifiedversion of the signal.
 2. The acoustic physiological monitor of claim 1,wherein adjusting the one or more signal processing parameters comprisescalculating, based on the first characteristic and the secondcharacteristic, an inverse of a transfer function associated with eachof at least the first stage and the second stage.
 3. The acousticphysiological monitor of claim 2, wherein generating a modified versionof the signal comprises applying the inverse transfer function to thesignal.
 4. The acoustic physiological monitor of claim 1, wherein saidone or more hardware processors are further configured to automaticallyadjust the one or more signal processing parameters when a stage of themulti-stage sensor assembly is replaced.
 5. The acoustic physiologicalmonitor of claim 1, wherein the calibration information includes acut-off frequency associated with at least one of the first stage or thesecond stage.
 6. The acoustic physiological monitor of claim 5, whereinthe calibration information includes a cut-off frequency associated witheach of the first stage and the second stage.
 7. The acousticphysiological monitor of claim 1, wherein the calibration informationincludes process variable characteristics associated with at least oneof the first stage or the second stage.
 8. The acoustic physiologicalmonitor of claim 1, wherein the calibration information includes adesign variable characteristic associated with at least one of the firststage or the second stage.
 9. The acoustic physiological monitor ofclaim 1, wherein the calibration information includes at least one of asensitivity, a mechanical cut-in frequency, a mechanical cut-offfrequency, a capacitance, a gain, an input impedance, an outputimpedance, a minimum saturation level, a resistance, a linear curve, anon-linear curve, a response, or a transfer function.
 10. The acousticphysiological monitor of claim 1, wherein the second stage of themulti-stage sensor assembly comprises an acoustic sensor.
 11. Theacoustic physiological monitor of claim 1 further comprising a front endprocessor configured to condition the received signal for processing bysaid one or more hardware processors, wherein said one or more hardwareprocessors are further configured to adjust the one or more signalprocessing parameters of the signal processor based on calibrationinformation associated with the front end processor.
 12. The acousticphysiological monitor of claim 1, wherein the one or more hardwareprocessors are further configured to obtain authentication informationfrom at least one of the one or more electronic memories.
 13. A methodof determining an acoustic physiological parameter of a patient with anacoustic physiological monitor, the method comprising: receiving, via amulti-stage sensor assembly, a signal indicative of physiological soundsassociated with a patient, wherein the multi-stage sensor assemblyincludes at least a first stage and a second stage, wherein the firststage and the second stage are removably connected to one another, andto the acoustic physiological monitor, in a serial manner, wherein atleast one of the first stage or the second stage comprises a splittercable stage, and wherein the the splitter cable stage comprises: amonitor connector operative to connect to an acoustic physiologicalmonitor, a plurality of sensor connectors each operative to connect toone of a plurality of physiological sensors, and one or more decouplingcircuits operative to electrically decouple, from each other, sensorsconnected to the plurality of sensor connectors; obtaining calibrationinformation from data storage devices provided in each of at least thefirst stage and the second stage, the calibration information includingat least a first characteristic associated with the first stage and asecond characteristic associated with the second stage; adjusting one ormore parameters of a signal processing algorithm based on both the firstcharacteristic and the second characteristic to compensate forvariations in multi-stage sensor assembly components with saidcalibration information; based on the adjusted one or more parameters,generating a modified version of the signal indicative of physiologicalsounds associated with the patient; and determining an acousticphysiological parameter of the patient based upon the modified versionof the signal.
 14. The method of claim 13, further comprising receivingauthentication information associated with at least one of the firststage or the second stage.
 15. The method of claim 13, furthercomprising automatically adjusting the one or more signal processingparameters when a stage of the multi-stage sensor assembly is replaced.16. The method of claim 13, wherein determining the acousticphysiological parameter of the patient is also based upon calibrationinformation associated with a front end processor of the acousticphysiological monitor.
 17. The method of claim 13, wherein the firstcharacteristic or second characteristic includes at least one of anacoustic sensitivity, an acoustic mechanical cut-in frequency, anacoustic mechanical cut-off frequency, a capacitance, a gain, an inputimpedance, an output impedance, a minimum saturation level, aresistance, a linear curve, a non-linear curve, a response, or atransfer function.